java - 如何在 Java 中将 InputStream 读取/转换为字符串？

Question

如果你有一个java.io.InputStream对象，你应该如何处理那个对象并产生一个String？

假设我有一个InputStream包含文本数据的，我想将它转换为一个String，所以例如我可以将它写入一个日志文件。

InputStream获取并将其转换为的最简单方法是String什么？

public String convertStreamToString(InputStream is) {
    // ???
}

score 3130 · Accepted Answer

总结其他答案我发现了 11 种主要方法（见下文）。我写了一些性能测试（见下面的结果）：

将 InputStream 转换为字符串的方法：

使用IOUtils.toString（Apache 实用程序）

 String result = IOUtils.toString(inputStream, StandardCharsets.UTF_8);

使用CharStreams（番石榴）

 String result = CharStreams.toString(new InputStreamReader(
       inputStream, Charsets.UTF_8));

使用Scanner（JDK）

 Scanner s = new Scanner(inputStream).useDelimiter("\\A");
 String result = s.hasNext() ? s.next() : "";

使用流 API (Java 8)。警告：此解决方案将不同的换行符（如\r\n）转换为\n.

 String result = new BufferedReader(new InputStreamReader(inputStream))
   .lines().collect(Collectors.joining("\n"));

使用并行流 API (Java 8)。警告：此解决方案将不同的换行符（如\r\n）转换为\n.

 String result = new BufferedReader(new InputStreamReader(inputStream))
    .lines().parallel().collect(Collectors.joining("\n"));

使用InputStreamReader和StringBuilder（JDK）

 int bufferSize = 1024;
 char[] buffer = new char[bufferSize];
 StringBuilder out = new StringBuilder();
 Reader in = new InputStreamReader(stream, StandardCharsets.UTF_8);
 for (int numRead; (numRead = in.read(buffer, 0, buffer.length)) > 0; ) {
     out.append(buffer, 0, numRead);
 }
 return out.toString();

使用StringWriter和IOUtils.copy（Apache Commons）

 StringWriter writer = new StringWriter();
 IOUtils.copy(inputStream, writer, "UTF-8");
 return writer.toString();

使用ByteArrayOutputStream和inputStream.read（JDK）

 ByteArrayOutputStream result = new ByteArrayOutputStream();
 byte[] buffer = new byte[1024];
 for (int length; (length = inputStream.read(buffer)) != -1; ) {
     result.write(buffer, 0, length);
 }
 // StandardCharsets.UTF_8.name() > JDK 7
 return result.toString("UTF-8");

使用BufferedReader（JDK）。警告：此解决方案将不同的换行符（如\n\r）转换为line.separator系统属性（例如，在 Windows 中为“\r\n”）。

 String newLine = System.getProperty("line.separator");
 BufferedReader reader = new BufferedReader(
         new InputStreamReader(inputStream));
 StringBuilder result = new StringBuilder();
 for (String line; (line = reader.readLine()) != null; ) {
     if (result.length() > 0) {
         result.append(newLine);
     }
     result.append(line);
 }
 return result.toString();

使用BufferedInputStream和ByteArrayOutputStream（JDK）

BufferedInputStream bis = new BufferedInputStream(inputStream);
ByteArrayOutputStream buf = new ByteArrayOutputStream();
for (int result = bis.read(); result != -1; result = bis.read()) {
    buf.write((byte) result);
}
// StandardCharsets.UTF_8.name() > JDK 7
return buf.toString("UTF-8");

使用inputStream.read()和StringBuilder（JDK）。警告：此解决方案存在 Unicode 问题，例如俄语文本（仅适用于非 Unicode 文本）
```
StringBuilder sb = new StringBuilder();
for (int ch; (ch = inputStream.read()) != -1; ) {
    sb.append((char) ch);
}
return sb.toString();
```

警告：

解决方案 4、5 和 9 将不同的换行符转换为一个。
解决方案 11 无法正确处理 Unicode 文本

性能测试

small String(length = 175), url in github (mode = Average Time, system = Linux, score 1,343 最好)的性能测试：

              Benchmark                         Mode  Cnt   Score   Error  Units
 8. ByteArrayOutputStream and read (JDK)        avgt   10   1,343 ± 0,028  us/op
 6. InputStreamReader and StringBuilder (JDK)   avgt   10   6,980 ± 0,404  us/op
10. BufferedInputStream, ByteArrayOutputStream  avgt   10   7,437 ± 0,735  us/op
11. InputStream.read() and StringBuilder (JDK)  avgt   10   8,977 ± 0,328  us/op
 7. StringWriter and IOUtils.copy (Apache)      avgt   10  10,613 ± 0,599  us/op
 1. IOUtils.toString (Apache Utils)             avgt   10  10,605 ± 0,527  us/op
 3. Scanner (JDK)                               avgt   10  12,083 ± 0,293  us/op
 2. CharStreams (guava)                         avgt   10  12,999 ± 0,514  us/op
 4. Stream Api (Java 8)                         avgt   10  15,811 ± 0,605  us/op
 9. BufferedReader (JDK)                        avgt   10  16,038 ± 0,711  us/op
 5. parallel Stream Api (Java 8)                avgt   10  21,544 ± 0,583  us/op

big String(length = 50100), url in github (mode = Average Time, system = Linux, score 200,715 最好)的性能测试：

               Benchmark                        Mode  Cnt   Score        Error  Units
 8. ByteArrayOutputStream and read (JDK)        avgt   10   200,715 ±   18,103  us/op
 1. IOUtils.toString (Apache Utils)             avgt   10   300,019 ±    8,751  us/op
 6. InputStreamReader and StringBuilder (JDK)   avgt   10   347,616 ±  130,348  us/op
 7. StringWriter and IOUtils.copy (Apache)      avgt   10   352,791 ±  105,337  us/op
 2. CharStreams (guava)                         avgt   10   420,137 ±   59,877  us/op
 9. BufferedReader (JDK)                        avgt   10   632,028 ±   17,002  us/op
 5. parallel Stream Api (Java 8)                avgt   10   662,999 ±   46,199  us/op
 4. Stream Api (Java 8)                         avgt   10   701,269 ±   82,296  us/op
10. BufferedInputStream, ByteArrayOutputStream  avgt   10   740,837 ±    5,613  us/op
 3. Scanner (JDK)                               avgt   10   751,417 ±   62,026  us/op
11. InputStream.read() and StringBuilder (JDK)  avgt   10  2919,350 ± 1101,942  us/op

图表（性能测试取决于 Windows 7 系统中的输入流长度）

性能测试（平均时间）取决于 Windows 7 系统中的输入流长度：

 length  182    546     1092    3276    9828    29484   58968

 test8  0.38    0.938   1.868   4.448   13.412  36.459  72.708
 test4  2.362   3.609   5.573   12.769  40.74   81.415  159.864
 test5  3.881   5.075   6.904   14.123  50.258  129.937 166.162
 test9  2.237   3.493   5.422   11.977  45.98   89.336  177.39
 test6  1.261   2.12    4.38    10.698  31.821  86.106  186.636
 test7  1.601   2.391   3.646   8.367   38.196  110.221 211.016
 test1  1.529   2.381   3.527   8.411   40.551  105.16  212.573
 test3  3.035   3.934   8.606   20.858  61.571  118.744 235.428
 test2  3.136   6.238   10.508  33.48   43.532  118.044 239.481
 test10 1.593   4.736   7.527   20.557  59.856  162.907 323.147
 test11 3.913   11.506  23.26   68.644  207.591 600.444 1211.545

score 2724 · Accepted Answer

一个很好的方法是使用Apache commons IOUtils将其复制InputStream到StringWriter... 之类的

StringWriter writer = new StringWriter();
IOUtils.copy(inputStream, writer, encoding);
String theString = writer.toString();

甚至

// NB: does not close inputStream, you'll have to use try-with-resources for that
String theString = IOUtils.toString(inputStream, encoding);

或者，ByteArrayOutputStream如果您不想混合使用 Streams 和 Writers ，则可以使用

score 2343 · Accepted Answer

这是一种仅使用标准 Java 库的方法（请注意，流未关闭，您的里程可能会有所不同）。

static String convertStreamToString(java.io.InputStream is) {
    java.util.Scanner s = new java.util.Scanner(is).useDelimiter("\\A");
    return s.hasNext() ? s.next() : "";
}

我从“愚蠢的扫描仪技巧”文章中学到了这个技巧。它起作用的原因是因为Scanner迭代流中的标记，在这种情况下，我们使用“输入边界的开始”（\A）分隔标记，因此只为流的全部内容提供一个标记。

注意，如果您需要具体说明输入流的编码，您可以向Scanner构造函数提供第二个参数，指示要使用的字符集（例如“UTF-8”）。

帽子小费也送给雅各布，他曾经向我指出上述文章。

score 876 · Accepted Answer

Apache Commons 允许：

String myString = IOUtils.toString(myInputStream, "UTF-8");

当然，您可以选择除 UTF-8 之外的其他字符编码。

另见：（文档）

score 311 · Accepted Answer

考虑到文件一个应该首先得到一个java.io.Reader实例。然后可以读取它并将其添加到 a （如果我们不在多个线程中访问它，我们StringBuilder不需要，并且速度更快）。这里的诀窍是我们在块中工作，因此不需要其他缓冲流。块大小被参数化以用于运行时性能优化。StringBufferStringBuilder

public static String slurp(final InputStream is, final int bufferSize) {
    final char[] buffer = new char[bufferSize];
    final StringBuilder out = new StringBuilder();
    try (Reader in = new InputStreamReader(is, "UTF-8")) {
        for (;;) {
            int rsz = in.read(buffer, 0, buffer.length);
            if (rsz < 0)
                break;
            out.append(buffer, 0, rsz);
        }
    }
    catch (UnsupportedEncodingException ex) {
        /* ... */
    }
    catch (IOException ex) {
        /* ... */
    }
    return out.toString();
}

score 263 · Accepted Answer

采用：

InputStream in = /* Your InputStream */;
StringBuilder sb = new StringBuilder();
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String read;

while ((read=br.readLine()) != null) {
    //System.out.println(read);
    sb.append(read);
}

br.close();
return sb.toString();

score 177 · Accepted Answer

如果您使用的是 Google-Collections/Guava，您可以执行以下操作：

InputStream stream = ...
String content = CharStreams.toString(new InputStreamReader(stream, Charsets.UTF_8));
Closeables.closeQuietly(stream);

请注意，第二个参数（即 Charsets.UTF_8）InputStreamReader不是必需的，但如果您知道编码，通常最好指定编码（您应该这样做！）

score 145 · Accepted Answer

为了完整起见，这里是Java 9解决方案：

public static String toString(InputStream input) throws IOException {
    return new String(input.readAllBytes(), StandardCharsets.UTF_8);
}

这使用了readAllBytes添加到 Java 9 中的方法。

score 132 · Accepted Answer

这是最适合 Android 和任何其他 JVM 的纯 Java 解决方案。

这个解决方案运行得非常好......它简单、快速，并且在大小流上都一样！（见上面的基准.. 8 号）

public String readFullyAsString(InputStream inputStream, String encoding)
        throws IOException {
    return readFully(inputStream).toString(encoding);
}

public byte[] readFullyAsBytes(InputStream inputStream)
        throws IOException {
    return readFully(inputStream).toByteArray();
}

private ByteArrayOutputStream readFully(InputStream inputStream)
        throws IOException {
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    byte[] buffer = new byte[1024];
    int length = 0;
    while ((length = inputStream.read(buffer)) != -1) {
        baos.write(buffer, 0, length);
    }
    return baos;
}

score 73 · Accepted Answer

采用：

import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.IOException;

public static String readInputStreamAsString(InputStream in)
    throws IOException {

    BufferedInputStream bis = new BufferedInputStream(in);
    ByteArrayOutputStream buf = new ByteArrayOutputStream();
    int result = bis.read();
    while(result != -1) {
      byte b = (byte)result;
      buf.write(b);
      result = bis.read();
    }
    return buf.toString();
}

score 66 · Accepted Answer

这是我经过一些实验后想出的最优雅的纯 Java（无库）解决方案：

public static String fromStream(InputStream in) throws IOException
{
    BufferedReader reader = new BufferedReader(new InputStreamReader(in));
    StringBuilder out = new StringBuilder();
    String newLine = System.getProperty("line.separator");
    String line;
    while ((line = reader.readLine()) != null) {
        out.append(line);
        out.append(newLine);
    }
    return out.toString();
}

score 61 · Accepted Answer

我在这里对 14 个不同的答案进行了基准测试（很抱歉没有提供学分，但重复的太多了）。

结果非常令人惊讶。事实证明，Apache IOUtils是最慢的，ByteArrayOutputStream也是最快的解决方案：

所以首先这里是最好的方法：

public String inputStreamToString(InputStream inputStream) throws IOException {
    try(ByteArrayOutputStream result = new ByteArrayOutputStream()) {
        byte[] buffer = new byte[1024];
        int length;
        while ((length = inputStream.read(buffer)) != -1) {
            result.write(buffer, 0, length);
        }

        return result.toString(UTF_8);
    }
}

20 个周期内 20 MB 随机字节的基准测试结果

以毫秒为单位的时间

字节数组输出流测试：194
NioStream：198
Java9ISTransferTo：201
Java9ISReadAllBytes：205
BufferedInputStreamVsByteArrayOutputStream：314
ApacheStringWriter2：574
GuavaCharStreams：589
ScannerReaderNoNextTest: 614
扫描仪阅读器：633
ApacheStringWriter：1544
StreamApi：错误
ParallelStreamApi：错误
BufferReaderTest：错误
InputStreamAndStringBuilder：错误

基准测试源代码

import com.google.common.io.CharStreams;
import org.apache.commons.io.IOUtils;

import java.io.*;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.WritableByteChannel;
import java.util.Arrays;
import java.util.List;
import java.util.Random;
import java.util.stream.Collectors;

/**
 * Created by Ilya Gazman on 2/13/18.
 */
public class InputStreamToString {


    private static final String UTF_8 = "UTF-8";

    public static void main(String... args) {
        log("App started");
        byte[] bytes = new byte[1024 * 1024];
        new Random().nextBytes(bytes);
        log("Stream is ready\n");

        try {
            test(bytes);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static void test(byte[] bytes) throws IOException {
        List<Stringify> tests = Arrays.asList(
                new ApacheStringWriter(),
                new ApacheStringWriter2(),
                new NioStream(),
                new ScannerReader(),
                new ScannerReaderNoNextTest(),
                new GuavaCharStreams(),
                new StreamApi(),
                new ParallelStreamApi(),
                new ByteArrayOutputStreamTest(),
                new BufferReaderTest(),
                new BufferedInputStreamVsByteArrayOutputStream(),
                new InputStreamAndStringBuilder(),
                new Java9ISTransferTo(),
                new Java9ISReadAllBytes()
        );

        String solution = new String(bytes, "UTF-8");

        for (Stringify test : tests) {
            try (ByteArrayInputStream inputStream = new ByteArrayInputStream(bytes)) {
                String s = test.inputStreamToString(inputStream);
                if (!s.equals(solution)) {
                    log(test.name() + ": Error");
                    continue;
                }
            }
            long startTime = System.currentTimeMillis();
            for (int i = 0; i < 20; i++) {
                try (ByteArrayInputStream inputStream = new ByteArrayInputStream(bytes)) {
                    test.inputStreamToString(inputStream);
                }
            }
            log(test.name() + ": " + (System.currentTimeMillis() - startTime));
        }
    }

    private static void log(String message) {
        System.out.println(message);
    }

    interface Stringify {
        String inputStreamToString(InputStream inputStream) throws IOException;

        default String name() {
            return this.getClass().getSimpleName();
        }
    }

    static class ApacheStringWriter implements Stringify {

        @Override
        public String inputStreamToString(InputStream inputStream) throws IOException {
            StringWriter writer = new StringWriter();
            IOUtils.copy(inputStream, writer, UTF_8);
            return writer.toString();
        }
    }

    static class ApacheStringWriter2 implements Stringify {

        @Override
        public String inputStreamToString(InputStream inputStream) throws IOException {
            return IOUtils.toString(inputStream, UTF_8);
        }
    }

    static class NioStream implements Stringify {

        @Override
        public String inputStreamToString(InputStream in) throws IOException {
            ReadableByteChannel channel = Channels.newChannel(in);
            ByteBuffer byteBuffer = ByteBuffer.allocate(1024 * 16);
            ByteArrayOutputStream bout = new ByteArrayOutputStream();
            WritableByteChannel outChannel = Channels.newChannel(bout);
            while (channel.read(byteBuffer) > 0 || byteBuffer.position() > 0) {
                byteBuffer.flip();  //make buffer ready for write
                outChannel.write(byteBuffer);
                byteBuffer.compact(); //make buffer ready for reading
            }
            channel.close();
            outChannel.close();
            return bout.toString(UTF_8);
        }
    }

    static class ScannerReader implements Stringify {

        @Override
        public String inputStreamToString(InputStream is) throws IOException {
            java.util.Scanner s = new java.util.Scanner(is).useDelimiter("\\A");
            return s.hasNext() ? s.next() : "";
        }
    }

    static class ScannerReaderNoNextTest implements Stringify {

        @Override
        public String inputStreamToString(InputStream is) throws IOException {
            java.util.Scanner s = new java.util.Scanner(is).useDelimiter("\\A");
            return s.next();
        }
    }

    static class GuavaCharStreams implements Stringify {

        @Override
        public String inputStreamToString(InputStream is) throws IOException {
            return CharStreams.toString(new InputStreamReader(
                    is, UTF_8));
        }
    }

    static class StreamApi implements Stringify {

        @Override
        public String inputStreamToString(InputStream inputStream) throws IOException {
            return new BufferedReader(new InputStreamReader(inputStream))
                    .lines().collect(Collectors.joining("\n"));
        }
    }

    static class ParallelStreamApi implements Stringify {

        @Override
        public String inputStreamToString(InputStream inputStream) throws IOException {
            return new BufferedReader(new InputStreamReader(inputStream)).lines()
                    .parallel().collect(Collectors.joining("\n"));
        }
    }

    static class ByteArrayOutputStreamTest implements Stringify {

        @Override
        public String inputStreamToString(InputStream inputStream) throws IOException {
            try(ByteArrayOutputStream result = new ByteArrayOutputStream()) {
                byte[] buffer = new byte[1024];
                int length;
                while ((length = inputStream.read(buffer)) != -1) {
                    result.write(buffer, 0, length);
                }

                return result.toString(UTF_8);
            }
        }
    }

    static class BufferReaderTest implements Stringify {

        @Override
        public String inputStreamToString(InputStream inputStream) throws IOException {
            String newLine = System.getProperty("line.separator");
            BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
            StringBuilder result = new StringBuilder(UTF_8);
            String line;
            boolean flag = false;
            while ((line = reader.readLine()) != null) {
                result.append(flag ? newLine : "").append(line);
                flag = true;
            }
            return result.toString();
        }
    }

    static class BufferedInputStreamVsByteArrayOutputStream implements Stringify {

        @Override
        public String inputStreamToString(InputStream inputStream) throws IOException {
            BufferedInputStream bis = new BufferedInputStream(inputStream);
            ByteArrayOutputStream buf = new ByteArrayOutputStream();
            int result = bis.read();
            while (result != -1) {
                buf.write((byte) result);
                result = bis.read();
            }

            return buf.toString(UTF_8);
        }
    }

    static class InputStreamAndStringBuilder implements Stringify {

        @Override
        public String inputStreamToString(InputStream inputStream) throws IOException {
            int ch;
            StringBuilder sb = new StringBuilder(UTF_8);
            while ((ch = inputStream.read()) != -1)
                sb.append((char) ch);
            return sb.toString();
        }
    }

    static class Java9ISTransferTo implements Stringify {

        @Override
        public String inputStreamToString(InputStream inputStream) throws IOException {
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            inputStream.transferTo(bos);
            return bos.toString(UTF_8);
        }
    }

    static class Java9ISReadAllBytes implements Stringify {

        @Override
        public String inputStreamToString(InputStream inputStream) throws IOException {
            return new String(inputStream.readAllBytes(), UTF_8);
        }
    }

}

score 41 · Accepted Answer

我会使用一些 Java 8 技巧。

public static String streamToString(final InputStream inputStream) throws Exception {
    // buffering optional
    try
    (
        final BufferedReader br
           = new BufferedReader(new InputStreamReader(inputStream))
    ) {
        // parallel optional
        return br.lines().parallel().collect(Collectors.joining("\n"));
    } catch (final IOException e) {
        throw new RuntimeException(e);
        // whatever.
    }
}

除了更简洁之外，与其他一些答案基本相同。

score 37 · Accepted Answer

我进行了一些计时测试，因为时间总是很重要。

我试图以 3 种不同的方式将响应转换为字符串。（如下所示）
为了便于阅读，我省略了 try/catch 块。

为了给出上下文，这是所有 3 种方法的前面代码：

   String response;
   String url = "www.blah.com/path?key=value";
   GetMethod method = new GetMethod(url);
   int status = client.executeMethod(method);

1)

 response = method.getResponseBodyAsString();

2)

InputStream resp = method.getResponseBodyAsStream();
InputStreamReader is=new InputStreamReader(resp);
BufferedReader br=new BufferedReader(is);
String read = null;
StringBuffer sb = new StringBuffer();
while((read = br.readLine()) != null) {
    sb.append(read);
}
response = sb.toString();

3)

InputStream iStream  = method.getResponseBodyAsStream();
StringWriter writer = new StringWriter();
IOUtils.copy(iStream, writer, "UTF-8");
response = writer.toString();

因此，在使用相同的请求/响应数据对每种方法运行 500 次测试之后，这里是数字。再一次，这些是我的发现，你的发现可能并不完全相同，但我写这篇文章是为了向其他人说明这些方法的效率差异。

排名：
方法 #1
方法 #3 - 比 #1 慢 2.6%
方法 #2 - 比 #1 慢 4.3%

这些方法中的任何一种都是获取响应并从中创建字符串的合适解决方案。

score 36 · Accepted Answer

使用Stream的纯 Java 解决方案，从 Java 8 开始工作。

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.stream.Collectors;

// ...
public static String inputStreamToString(InputStream is) throws IOException {
    try (BufferedReader br = new BufferedReader(new InputStreamReader(is))) {
        return br.lines().collect(Collectors.joining(System.lineSeparator()));
    }
}

正如 Christoffer Hammarström 在其他答案下面所提到的，明确指定Charset更安全。即 InputStreamReader 构造函数可以更改如下：

new InputStreamReader(is, Charset.forName("UTF-8"))

score 28 · Accepted Answer

这里或多或少是 sampath 的答案，稍微清理一下并表示为一个函数：

String streamToString(InputStream in) throws IOException {
  StringBuilder out = new StringBuilder();
  BufferedReader br = new BufferedReader(new InputStreamReader(in));
  for(String line = br.readLine(); line != null; line = br.readLine()) 
    out.append(line);
  br.close();
  return out.toString();
}

score 27 · Accepted Answer

如果您喜欢冒险，您可以混合使用 Scala 和 Java，然后得到以下结果：

scala.io.Source.fromInputStream(is).mkString("")

混合 Java 和 Scala 代码和库有它的好处。

在此处查看完整描述：Idiomatic way to convert an InputStream to a String in Scala

score 26 · Accepted Answer

如果您不能使用 Commons IO (FileUtils/IOUtils/CopyUtils)，下面是一个使用 BufferedReader 逐行读取文件的示例：

public class StringFromFile {
    public static void main(String[] args) /*throws UnsupportedEncodingException*/ {
        InputStream is = StringFromFile.class.getResourceAsStream("file.txt");
        BufferedReader br = new BufferedReader(new InputStreamReader(is/*, "UTF-8"*/));
        final int CHARS_PER_PAGE = 5000; //counting spaces
        StringBuilder builder = new StringBuilder(CHARS_PER_PAGE);
        try {
            for(String line=br.readLine(); line!=null; line=br.readLine()) {
                builder.append(line);
                builder.append('\n');
            }
        } 
        catch (IOException ignore) { }

        String text = builder.toString();
        System.out.println(text);
    }
}

或者，如果您想要原始速度，我会提出 Paul de Vrieze 建议的变体（避免使用 StringWriter（在内部使用 StringBuffer）：

public class StringFromFileFast {
    public static void main(String[] args) /*throws UnsupportedEncodingException*/ {
        InputStream is = StringFromFileFast.class.getResourceAsStream("file.txt");
        InputStreamReader input = new InputStreamReader(is/*, "UTF-8"*/);
        final int CHARS_PER_PAGE = 5000; //counting spaces
        final char[] buffer = new char[CHARS_PER_PAGE];
        StringBuilder output = new StringBuilder(CHARS_PER_PAGE);
        try {
            for(int read = input.read(buffer, 0, buffer.length);
                    read != -1;
                    read = input.read(buffer, 0, buffer.length)) {
                output.append(buffer, 0, read);
            }
        } catch (IOException ignore) { }

        String text = output.toString();
        System.out.println(text);
    }
}

score 21 · Accepted Answer

使用Java 9 中支持的java.io.InputStream.transferTo(OutputStream)和采用字符集名称的ByteArrayOutputStream.toString(String) ：

public static String gobble(InputStream in, String charsetName) throws IOException {
    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    in.transferTo(bos);
    return bos.toString(charsetName);
}

score 20 · Accepted Answer

如果您使用流阅读器，请确保在最后关闭流

private String readStream(InputStream iStream) throws IOException {
    //build a Stream Reader, it can read char by char
    InputStreamReader iStreamReader = new InputStreamReader(iStream);
    //build a buffered Reader, so that i can read whole line at once
    BufferedReader bReader = new BufferedReader(iStreamReader);
    String line = null;
    StringBuilder builder = new StringBuilder();
    while((line = bReader.readLine()) != null) {  //Read till end
        builder.append(line);
        builder.append("\n"); // append new line to preserve lines
    }
    bReader.close();         //close all opened stuff
    iStreamReader.close();
    //iStream.close(); //EDIT: Let the creator of the stream close it!
                       // some readers may auto close the inner stream
    return builder.toString();
}

编辑：在 JDK 7+ 上，您可以使用 try-with-resources 构造。

/**
 * Reads the stream into a string
 * @param iStream the input stream
 * @return the string read from the stream
 * @throws IOException when an IO error occurs
 */
private String readStream(InputStream iStream) throws IOException {

    //Buffered reader allows us to read line by line
    try (BufferedReader bReader =
                 new BufferedReader(new InputStreamReader(iStream))){
        StringBuilder builder = new StringBuilder();
        String line;
        while((line = bReader.readLine()) != null) {  //Read till end
            builder.append(line);
            builder.append("\n"); // append new line to preserve lines
        }
        return builder.toString();
    }
}

score 19 · Accepted Answer

这个很好，因为：

它安全地处理字符集。
您可以控制读取缓冲区的大小。
您可以设置构建器的长度，它不必是精确值。
没有库依赖。
适用于 Java 7 或更高版本。

怎么做？

public static String convertStreamToString(InputStream is) throws IOException {
   StringBuilder sb = new StringBuilder(2048); // Define a size if you have an idea of it.
   char[] read = new char[128]; // Your buffer size.
   try (InputStreamReader ir = new InputStreamReader(is, StandardCharsets.UTF_8)) {
     for (int i; -1 != (i = ir.read(read)); sb.append(read, 0, i));
   }
   return sb.toString();
}

对于 JDK 9

public static String inputStreamString(InputStream inputStream) throws IOException {
    try (inputStream) {
        return new String(inputStream.readAllBytes(), StandardCharsets.UTF_8);
    }
}

score 19 · Accepted Answer

org.apache.commons.io.IOUtils 这是改编自源代码的答案，适用于那些想要 apache 实现但不想要整个库的人。

private static final int BUFFER_SIZE = 4 * 1024;

public static String inputStreamToString(InputStream inputStream, String charsetName)
        throws IOException {
    StringBuilder builder = new StringBuilder();
    InputStreamReader reader = new InputStreamReader(inputStream, charsetName);
    char[] buffer = new char[BUFFER_SIZE];
    int length;
    while ((length = reader.read(buffer)) != -1) {
        builder.append(buffer, 0, length);
    }
    return builder.toString();
}

score 19 · Accepted Answer

String inputStreamToString(InputStream inputStream, Charset charset) throws IOException {
    try (
            final StringWriter writer = new StringWriter();
            final InputStreamReader reader = new InputStreamReader(inputStream, charset)
        ) {
        reader.transferTo(writer);
        return writer.toString();
    }
}

纯 Java 标准库解决方案 - 无库
从 Java 10 开始 - Reader#transferTo(java.io.Writer)
无环解决方案
没有换行符处理

score 17 · Accepted Answer

另一个，适用于所有 Spring 用户：

import java.nio.charset.StandardCharsets;
import org.springframework.util.FileCopyUtils;

public String convertStreamToString(InputStream is) throws IOException { 
    return new String(FileCopyUtils.copyToByteArray(is), StandardCharsets.UTF_8);
}

中的实用方法org.springframework.util.StreamUtils类似于中的实用方法FileCopyUtils，但它们在完成时使流保持打开状态。

score 16 · Accepted Answer

这是在不使用任何第三方库的情况下转换InputStream为的完整方法。String用于StringBuilder单线程环境，否则使用StringBuffer.

public static String getString( InputStream is) throws IOException {
    int ch;
    StringBuilder sb = new StringBuilder();
    while((ch = is.read()) != -1)
        sb.append((char)ch);
    return sb.toString();
}

score 16 · Accepted Answer

Kotlin 用户只需执行以下操作：

println(InputStreamReader(is).readText())

然而

readText()

是 Kotlin 标准库的内置扩展方法。

score 15 · Accepted Answer

以下是使用字节数组缓冲区仅使用 JDK 的方法。这实际上是 commons-ioIOUtils.copy()方法的全部工作方式。如果您从 a而不是复制，则可以替换byte[]为。char[]ReaderInputStream

import java.io.ByteArrayOutputStream;
import java.io.InputStream;

...

InputStream is = ....
ByteArrayOutputStream baos = new ByteArrayOutputStream(8192);
byte[] buffer = new byte[8192];
int count = 0;
try {
  while ((count = is.read(buffer)) != -1) {
    baos.write(buffer, 0, count);
  }
}
finally {
  try {
    is.close();
  }
  catch (Exception ignore) {
  }
}

String charset = "UTF-8";
String inputStreamAsString = baos.toString(charset);

score 10 · Accepted Answer

JDK 中最简单的方法是使用以下代码片段。

String convertToString(InputStream in){
    String resource = new Scanner(in).useDelimiter("\\Z").next();
    return resource;
}

score 9 · Accepted Answer

用reduce,concat在 Java 8 中可以表示为：

String fromFile = new BufferedReader(new   
InputStreamReader(inputStream)).lines().reduce(String::concat).get();

score 8 · Accepted Answer

这是我的基于Java 8的解决方案，它使用新的 Stream API从以下位置收集所有行InputStream：

public static String toString(InputStream inputStream) {
    BufferedReader reader = new BufferedReader(
        new InputStreamReader(inputStream));
    return reader.lines().collect(Collectors.joining(
        System.getProperty("line.separator")));
}

score 5 · Accepted Answer

下面的代码对我有用。

URL url = MyClass.class.getResource("/" + configFileName);
BufferedInputStream bi = (BufferedInputStream) url.getContent();
byte[] buffer = new byte[bi.available() ];
int bytesRead = bi.read(buffer);
String out = new String(buffer);

请注意，根据 Java 文档，该available()方法可能不适用于InputStream但始终适用于BufferedInputStream. 如果您不想使用available()方法，我们可以随时使用以下代码

URL url = MyClass.class.getResource("/" + configFileName);
BufferedInputStream bi = (BufferedInputStream) url.getContent();
File f = new File(url.getPath());
byte[] buffer = new byte[ (int) f.length()];
int bytesRead = bi.read(buffer);
String out = new String(buffer);

我不确定是否会有任何编码问题。请评论，如果代码有任何问题。

score 5 · Accepted Answer

好吧，你可以自己编程......这并不复杂......

String Inputstream2String (InputStream is) throws IOException
    {
        final int PKG_SIZE = 1024;
        byte[] data = new byte [PKG_SIZE];
        StringBuilder buffer = new StringBuilder(PKG_SIZE * 10);
        int size;

        size = is.read(data, 0, data.length);
        while (size > 0)
        {
            String str = new String(data, 0, size);
            buffer.append(str);
            size = is.read(data, 0, data.length);
        }
        return buffer.toString();
    }

score 5 · Accepted Answer

JDK 7/8 答案关闭了流并仍然抛出 IOException：

StringBuilder build = new StringBuilder();
byte[] buf = new byte[1024];
int length;
try (InputStream is = getInputStream()) {
  while ((length = is.read(buf)) != -1) {
    build.append(new String(buf, 0, length));
  }
}

score 5 · Accepted Answer

我写了一个可以做到这一点的课程，所以我想我会与大家分享。有时您不想仅仅为了一件事而添加 Apache Commons，并且想要比不检查内容的 Scanner 更愚蠢的东西。

用法如下

// Read from InputStream
String data = new ReaderSink(inputStream, Charset.forName("UTF-8")).drain();

// Read from File
data = new ReaderSink(file, Charset.forName("UTF-8")).drain();

// Drain input stream to console
new ReaderSink(inputStream, Charset.forName("UTF-8")).drainTo(System.out);

这是 ReaderSink 的代码：

import java.io.*;
import java.nio.charset.Charset;

/**
 * A simple sink class that drains a {@link Reader} to a {@link String} or
 * to a {@link Writer}.
 *
 * @author Ben Barkay
 * @version 2/20/2014
 */
public class ReaderSink {
    /**
     * The default buffer size to use if no buffer size was specified.
     */
    public static final int DEFAULT_BUFFER_SIZE = 1024;

    /**
     * The {@link Reader} that will be drained.
     */
    private final Reader in;

    /**
     * Constructs a new {@code ReaderSink} for the specified file and charset.
     * @param file      The file to read from.
     * @param charset   The charset to use.
     * @throws FileNotFoundException    If the file was not found on the filesystem.
     */
    public ReaderSink(File file, Charset charset) throws FileNotFoundException {
        this(new FileInputStream(file), charset);
    }

    /**
     * Constructs a new {@code ReaderSink} for the specified {@link InputStream}.
     * @param in        The {@link InputStream} to drain.
     * @param charset   The charset to use.
     */
    public ReaderSink(InputStream in, Charset charset) {
        this(new InputStreamReader(in, charset));
    }

    /**
     * Constructs a new {@code ReaderSink} for the specified {@link Reader}.
     * @param in    The reader to drain.
     */
    public ReaderSink(Reader in) {
        this.in = in;
    }

    /**
     * Drains the data from the underlying {@link Reader}, returning a {@link String} containing
     * all of the read information. This method will use {@link #DEFAULT_BUFFER_SIZE} for
     * its buffer size.
     * @return  A {@link String} containing all of the information that was read.
     */
    public String drain() throws IOException {
        return drain(DEFAULT_BUFFER_SIZE);
    }

    /**
     * Drains the data from the underlying {@link Reader}, returning a {@link String} containing
     * all of the read information.
     * @param bufferSize    The size of the buffer to use when reading.
     * @return  A {@link String} containing all of the information that was read.
     */
    public String drain(int bufferSize) throws IOException {
        StringWriter stringWriter = new StringWriter();
        drainTo(stringWriter, bufferSize);
        return stringWriter.toString();
    }

    /**
     * Drains the data from the underlying {@link Reader}, writing it to the
     * specified {@link Writer}. This method will use {@link #DEFAULT_BUFFER_SIZE} for
     * its buffer size.
     * @param out   The {@link Writer} to write to.
     */
    public void drainTo(Writer out) throws IOException {
        drainTo(out, DEFAULT_BUFFER_SIZE);
    }

    /**
     * Drains the data from the underlying {@link Reader}, writing it to the
     * specified {@link Writer}.
     * @param out           The {@link Writer} to write to.
     * @param bufferSize    The size of the buffer to use when reader.
     */
    public void drainTo(Writer out, int bufferSize) throws IOException {
        char[] buffer = new char[bufferSize];
        int read;
        while ((read = in.read(buffer)) > -1) {
            out.write(buffer, 0, read);
        }
    }
}

score 5 · Accepted Answer

基于已接受的 Apache Commons 答案的第二部分，但填补了始终关闭流的小空白：

    String theString;
    try {
        theString = IOUtils.toString(inputStream, encoding);
    } finally {
        IOUtils.closeQuietly(inputStream);
    }

score 4 · Accepted Answer

您可以使用 Apache Commons。

在 IOUtils 中，您可以找到具有三个有用实现的 toString 方法。

public static String toString(InputStream input) throws IOException {
        return toString(input, Charset.defaultCharset());
}

public static String toString(InputStream input) throws IOException {
        return toString(input, Charset.defaultCharset());
}

public static String toString(InputStream input, String encoding)
            throws IOException {
        return toString(input, Charsets.toCharset(encoding));
}

score 4 · Accepted Answer

试试这4个语句..

根据 Fred 回忆的观点，不建议附加Stringwith+=运算符，因为每次将新对象char附加到现有对象时，都会再次String创建一个新String对象并将其地址分配给st旧st对象成为垃圾。

public String convertStreamToString(InputStream is)
{
    int k;
    StringBuffer sb=new StringBuffer();
    while((k=fin.read()) != -1)
    {
        sb.append((char)k);
    }
    return sb.toString();
}

不推荐，但这也是一种方式

public String convertStreamToString(InputStream is) { 
    int k;
    String st="";
    while((k=is.read()) != -1)
    {
        st+=(char)k;
    }
    return st;
}

score 4 · Accepted Answer

InputStream is = Context.openFileInput(someFileName); // whatever format you have

ByteArrayOutputStream bos = new ByteArrayOutputStream();

byte[] b = new byte[8192];
for (int bytesRead; (bytesRead = is.read(b)) != -1;) {
    bos.write(b, 0, bytesRead);
}

String output = bos.toString(someEncoding);

score 4 · Accepted Answer

如果输入流来自类路径资源（这似乎是流行的任务），Guava 提供了更短的高效自动关闭解决方案：

byte[] bytes = Resources.toByteArray(classLoader.getResource(path));

或者

String text = Resources.toString(classLoader.getResource(path), StandardCharsets.UTF_8);

还有ByteSource和CharSource的一般概念，它们温和地处理打开和关闭流。

因此，例如，不要显式打开一个小文件来读取其内容：

String content = Files.asCharSource(new File("robots.txt"), StandardCharsets.UTF_8).read();
byte[] data = Files.asByteSource(new File("favicon.ico")).read();

要不就

String content = Files.toString(new File("robots.txt"), StandardCharsets.UTF_8);
byte[] data = Files.toByteArray(new File("favicon.ico"));

score 4 · Accepted Answer

4

在 Groovy 中

inputStream.getText()

于 2017-01-26T19:40:23.513 回答

score 4 · Accepted Answer

Raghu K Nair是唯一使用扫描仪的人。我使用的代码有点不同：

String convertToString(InputStream in){
    Scanner scanner = new Scanner(in)
    scanner.useDelimiter("\\A");

    boolean hasInput = scanner.hasNext();
    if (hasInput) {
        return scanner.next();
    } else {
        return null;
    }

}

关于分隔符：如何在 Java Scanner 中使用分隔符？

score 3 · Accepted Answer

public String read(InputStream in) throws IOException {
    try (BufferedReader buffer = new BufferedReader(new InputStreamReader(in))) {
        return buffer.lines().collect(Collectors.joining("\n"));
    }
}

score 3 · Accepted Answer

3

与奥基奥：

String result = Okio.buffer(Okio.source(inputStream)).readUtf8();

于 2018-04-07T12:53:23.680 回答

score 2 · Accepted Answer

InputStreamReader i = new InputStreamReader(s);
BufferedReader str = new BufferedReader(i);
String msg = str.readLine();
System.out.println(msg);

这里 s 是你的InputStream对象，它将被转换成String

score 2 · Accepted Answer

您可以使用Cactoos：

String text = new TextOf(inputStream).asString();

UTF-8 编码是默认编码。如果您需要另一个：

String text = new TextOf(inputStream, "UTF-16").asString();

score 2 · Accepted Answer

我已经创建了这段代码，它可以工作。不需要外部插件。

有一个转换器StringtoStream和Streamto String：

import java.io.ByteArrayInputStream;
import java.io.InputStream;

public class STRINGTOSTREAM {

    public static void main(String[] args)
    {
        String text = "Hello Bhola..!\nMy Name Is Kishan ";

        InputStream strm = new ByteArrayInputStream(text.getBytes());    // Convert String to Stream

        String data = streamTostring(strm);

        System.out.println(data);
    }

    static String streamTostring(InputStream stream)
    {
        String data = "";

        try
        {
            StringBuilder stringbuld = new StringBuilder();
            int i;
            while ((i=stream.read())!=-1)
            {
                stringbuld.append((char)i);
            }
            data = stringbuld.toString();
        }
        catch(Exception e)
        {
            data = "No data Streamed.";
        }
        return data;
    }

score 2 · Accepted Answer

ISO-8859-1

如果您知道输入流的编码是 ISO-8859-1 或 ASCII，这是一种非常高效的方法。StringWriter它 (1) 避免了's internal中出现的不必要的同步StringBuffer，(2) 避免了的开销InputStreamReader，并且 (3) 最小化了StringBuilder's internalchar数组必须被复制的次数。

public static String iso_8859_1(InputStream is) throws IOException {
    StringBuilder chars = new StringBuilder(Math.max(is.available(), 4096));
    byte[] buffer = new byte[4096];
    int n;
    while ((n = is.read(buffer)) != -1) {
        for (int i = 0; i < n; i++) {
            chars.append((char)(buffer[i] & 0xFF));
        }
    }
    return chars.toString();
}

UTF-8

相同的通用策略可用于使用 UTF-8 编码的流：

public static String utf8(InputStream is) throws IOException {
    StringBuilder chars = new StringBuilder(Math.max(is.available(), 4096));
    byte[] buffer = new byte[4096];
    int n;
    int state = 0;
    while ((n = is.read(buffer)) != -1) {
        for (int i = 0; i < n; i++) {
            if ((state = nextStateUtf8(state, buffer[i])) >= 0) {
                chars.appendCodePoint(state);
            } else if (state == -1) { //error
                state = 0;
                chars.append('\uFFFD'); //replacement char
            }
        }
    }
    return chars.toString();
}

其中nextStateUtf8()函数定义如下：

/**
 * Returns the next UTF-8 state given the next byte of input and the current state.
 * If the input byte is the last byte in a valid UTF-8 byte sequence,
 * the returned state will be the corresponding unicode character (in the range of 0 through 0x10FFFF).
 * Otherwise, a negative integer is returned. A state of -1 is returned whenever an
 * invalid UTF-8 byte sequence is detected.
 */
static int nextStateUtf8(int currentState, byte nextByte) {
    switch (currentState & 0xF0000000) {
        case 0:
            if ((nextByte & 0x80) == 0) { //0 trailing bytes (ASCII)
                return nextByte;
            } else if ((nextByte & 0xE0) == 0xC0) { //1 trailing byte
                if (nextByte == (byte) 0xC0 || nextByte == (byte) 0xC1) { //0xCO & 0xC1 are overlong
                    return -1;
                } else {
                    return nextByte & 0xC000001F;
                }
            } else if ((nextByte & 0xF0) == 0xE0) { //2 trailing bytes
                if (nextByte == (byte) 0xE0) { //possibly overlong
                    return nextByte & 0xA000000F;
                } else if (nextByte == (byte) 0xED) { //possibly surrogate
                    return nextByte & 0xB000000F;
                } else {
                    return nextByte & 0x9000000F;
                }
            } else if ((nextByte & 0xFC) == 0xF0) { //3 trailing bytes
                if (nextByte == (byte) 0xF0) { //possibly overlong
                    return nextByte & 0x80000007;
                } else {
                    return nextByte & 0xE0000007;
                }
            } else if (nextByte == (byte) 0xF4) { //3 trailing bytes, possibly undefined
                return nextByte & 0xD0000007;
            } else {
                return -1;
            }
        case 0xE0000000: //3rd-to-last continuation byte
            return (nextByte & 0xC0) == 0x80 ? currentState << 6 | nextByte & 0x9000003F : -1;
        case 0x80000000: //3rd-to-last continuation byte, check overlong
            return (nextByte & 0xE0) == 0xA0 || (nextByte & 0xF0) == 0x90 ? currentState << 6 | nextByte & 0x9000003F : -1;
        case 0xD0000000: //3rd-to-last continuation byte, check undefined
            return (nextByte & 0xF0) == 0x80 ? currentState << 6 | nextByte & 0x9000003F : -1;
        case 0x90000000: //2nd-to-last continuation byte
            return (nextByte & 0xC0) == 0x80 ? currentState << 6 | nextByte & 0xC000003F : -1;
        case 0xA0000000: //2nd-to-last continuation byte, check overlong
            return (nextByte & 0xE0) == 0xA0 ? currentState << 6 | nextByte & 0xC000003F : -1;
        case 0xB0000000: //2nd-to-last continuation byte, check surrogate
            return (nextByte & 0xE0) == 0x80 ? currentState << 6 | nextByte & 0xC000003F : -1;
        case 0xC0000000: //last continuation byte
            return (nextByte & 0xC0) == 0x80 ? currentState << 6 | nextByte & 0x3F : -1;
        default:
            return -1;
    }
}

自动检测编码

如果您的输入流是使用 ASCII 或 ISO-8859-1 或 UTF-8 编码的，但您不确定是哪一个，我们可以使用与上一个类似的方法，但有一个额外的编码检测组件来自动检测返回字符串之前的编码。

public static String autoDetect(InputStream is) throws IOException {
    StringBuilder chars = new StringBuilder(Math.max(is.available(), 4096));
    byte[] buffer = new byte[4096];
    int n;
    int state = 0;
    boolean ascii = true;
    while ((n = is.read(buffer)) != -1) {
        for (int i = 0; i < n; i++) {
            if ((state = nextStateUtf8(state, buffer[i])) > 0x7F)
                ascii = false;
            chars.append((char)(buffer[i] & 0xFF));
        }
    }

    if (ascii || state < 0) { //probably not UTF-8
        return chars.toString();
    }
    //probably UTF-8
    int pos = 0;
    char[] charBuf = new char[2];
    for (int i = 0, len = chars.length(); i < len; i++) {
        if ((state = nextStateUtf8(state, (byte)chars.charAt(i))) >= 0) {
            boolean hi = Character.toChars(state, charBuf, 0) == 2;
            chars.setCharAt(pos++, charBuf[0]);
            if (hi) {
                chars.setCharAt(pos++, charBuf[1]);
            }
        }
    }
    return chars.substring(0, pos);
}

如果您的输入流的编码既不是 ISO-8859-1 也不是 ASCII 也不是 UTF-8，那么我会遵循已经存在的其他答案。

score 2 · Accepted Answer

此代码适用于新的 Java 学习者：

     private String textDataFromFile;

public String getFromFile(InputStream myInputStream) throws FileNotFoundException, IOException {

      BufferedReader bufferReader = new BufferedReader (new InputStreamReader(myInputStream));

       StringBuilder stringBuilder = new StringBuilder();

  String eachStringLine;

    while((eachStringLine=bufferReader.readLine()) != null){          
        stringBuilder.append(eachStringLine).append("\n");
    }

   textDataFromFile = stringBuilder.toString(); 



  return textDataFromFile;

}

score 2 · Accepted Answer

如果您需要将字符串转换为没有 外部库的特定字符集， 则：

public String convertStreamToString(InputStream is) throws IOException {
  try (ByteArrayOutputStream baos = new ByteArrayOutputStream();) {
    is.transferTo(baos);
    return baos.toString(StandardCharsets.UTF_8);
  }
}

score 1 · Accepted Answer

以下不解决原始问题，而是一些响应。

几个回应表明形式的循环

String line = null;
while((line = reader.readLine()) != null) {
  // ...
}

或者

for(String line = reader.readLine(); line != null; line = reader.readLine()) {
    // ...
}

第一种形式通过在封闭范围内声明一个变量“read”来污染封闭范围的命名空间，该变量不会用于 for 循环之外的任何内容。第二种形式复制了 readline() 调用。

这是用 Java 编写这种循环的一种更简洁的方法。事实证明，for 循环中的第一个子句不需要实际的初始值设定项。这将变量“line”的范围保持在 for 循环的主体内。优雅多了！我还没有看到任何人在任何地方使用过这种形式（我在几年前的一天偶然发现了它），但我一直都在使用它。

for (String line; (line = reader.readLine()) != null; ) {
    //...
}

score 1 · Accepted Answer

这个问题的解决方案不是最简单的，但是由于没有提到 NIO 流和通道，这里有一个使用 NIO 通道和 ByteBuffer 将流转换为字符串的版本。

public static String streamToStringChannel(InputStream in, String encoding, int bufSize) throws IOException {
    ReadableByteChannel channel = Channels.newChannel(in);
    ByteBuffer byteBuffer = ByteBuffer.allocate(bufSize);
    ByteArrayOutputStream bout = new ByteArrayOutputStream();
    WritableByteChannel outChannel = Channels.newChannel(bout);
    while (channel.read(byteBuffer) > 0 || byteBuffer.position() > 0) {
        byteBuffer.flip();  //make buffer ready for write
        outChannel.write(byteBuffer);
        byteBuffer.compact(); //make buffer ready for reading
    }
    channel.close();
    outChannel.close();
    return bout.toString(encoding);
}

这是一个如何使用它的示例：

try (InputStream in = new FileInputStream("/tmp/large_file.xml")) {
    String x = streamToStringChannel(in, "UTF-8", 1);
    System.out.println(x);
}

这种方法的性能应该对大文件有好处。

score 0 · Accepted Answer

此代码段位于 \sdk\samples\android-19\connectivity\NetworkConnect\NetworkConnectSample\src\main\java\com\example\android\networkconnect\MainActivity.java 中，该代码段已根据 Apache 许可证 2.0 版获得许可并由 Google 编写.

/** Reads an InputStream and converts it to a String.
 * @param stream InputStream containing HTML from targeted site.
 * @param len Length of string that this method returns.
 * @return String concatenated according to len parameter.
 * @throws java.io.IOException
 * @throws java.io.UnsupportedEncodingException
 */
private String readIt(InputStream stream, int len) throws IOException, UnsupportedEncodingException {
    Reader reader = null;
    reader = new InputStreamReader(stream, "UTF-8");
    char[] buffer = new char[len];
    reader.read(buffer);
    return new String(buffer);
}

score 0 · Accepted Answer

将 inputStream 转换为 String 的方法

public static String getStringFromInputStream(InputStream inputStream) {

    BufferedReader bufferedReader = null;
    StringBuilder stringBuilder = new StringBuilder();
    String line;

    try {
        bufferedReader = new BufferedReader(new InputStreamReader(
                inputStream));
        while ((line = bufferedReader.readLine()) != null) {
            stringBuilder.append(line);
        }
    } catch (IOException e) {
        logger.error(e.getMessage());
    } finally {
        if (bufferedReader != null) {
            try {
                bufferedReader.close();
            } catch (IOException e) {
                logger.error(e.getMessage());
            }
        }
    }
    return stringBuilder.toString();
}

score 0 · Accepted Answer

InputStream  inputStream = null;
BufferedReader bufferedReader = null;
try {
    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
    String stringBuilder = new StringBuilder();
    String content;
    while((content = bufferedReader.readLine()) != null){
        stringBuilder.append(content);
    }
    System.out.println("content of file::" + stringBuilder.toString());
}
catch (IOException e) {
            e.printStackTrace();
        }finally{           
            if(bufferedReader != null){
                try{
                    bufferedReader.close();
                }catch(IoException ex){
                   ex.printStackTrace();
            }

score 0 · Accepted Answer

您还可以从指定的资源路径获取 InputStream：

public static InputStream getResourceAsStream(String path)
{
    InputStream myiInputStream = ClassName.class.getResourceAsStream(path);
    if (null == myiInputStream)
    {
        mylogger.info("Can't find path = ", path);
    }

    return myiInputStream;
}

从特定路径获取 InputStream：

public static URL getResource(String path)
{
    URL myURL = ClassName.class.getResource(path);
    if (null == myURL)
    {
        mylogger.info("Can't find resource path = ", path);
    }
    return myURL;
}

score 0 · Accepted Answer

我建议使用StringWriter类来解决这个问题。

StringWriter wt= new StringWriter();
IOUtils.copy(inputStream, wt, encoding);
String st= wt.toString();

score -1 · Accepted Answer

我有可用的 log4j，所以我可以使用 org.apache.log4j.lf5.util.StreamUtils.getBytes 来获取字节，我可以使用 String ctor 将其转换为字符串

String result = new String(StreamUtils.getBytes(inputStream));

score -2 · Accepted Answer

注意：这可能不是一个好主意。此方法使用递归，因此会StackOverflowError很快达到：

public String read (InputStream is) {
    byte next = is.read();
    return next == -1 ? "" : next + read(is); // Recursive part: reads next byte recursively
}

score -2 · Accepted Answer

Dont want anyone to waste time on reading such structured response

Just showing signature of get api method
getMyData(KeyValueObject<String, List<String>> input){} which returns List<KeyValueObject<String, String>>
where KVO is like this

public class KeyValueObject<T, K> {
  private T key;
  private K value;
}

to make a call from another api and reading response 

Response response = ClientBuilder.newClient()
                    .target("https:/something")
                    .request(MediaType.APPLICATION_JSON)
.put(Entity.json(new KeyValueObject<>()));

            if (response != null && response.getStatus() == 200) {
                @SuppressWarnings("unchecked")
                KeyValueObject<String, String>[] output= response.readEntity(KeyValueObject[].class);
                
            }

score -2 · Accepted Answer

最简单的方法，一个班轮

 public static void main(String... args) throws IOException {
        System.out.println(new String(Files.readAllBytes(Paths.get("csv.txt"))));
    }

score -3 · Accepted Answer

  InputStream IS=new URL("http://www.petrol.si/api/gas_prices.json").openStream();   

  ByteArrayOutputStream BAOS=new ByteArrayOutputStream();
  IOUtils.copy(IS, BAOS);
  String d= new String(BAOS.toByteArray(),"UTF-8");           

System.out.println(d);

score -10 · Accepted Answer

-10

快捷方便：

String result = (String)new ObjectInputStream( inputStream ).readObject();

于 2012-07-19T17:33:39.780 回答

java - 如何在 Java 中将 InputStream 读取/转换为字符串？

62 回答 62

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