3

使用时出现异常StringReader。我在创建对象时解析的字符串是通过生成的String.split,它给了我NullPointerException。任何建议如何解决这个问题?

这是代码:

public static void main(String[] args) throws IOException {
    // TODO code application logic here
    int jmldoc = 5;
    Hashmap hashsentences[][] = new Hashmap[5][100];
    Docreader reader = new Docreader();
    System.out.println(reader.doc[1]);

    for (int i = 0; i < jmldoc; i++) {
        int j = 0;
        while (reader.sentences[i][j] != null) {
            System.out.println(reader.sentences[i][j]);
            j++;              
            String temp=reader.sentences[i][j];
            StringReader h = new StringReader(temp);

        }
    }


}

和 docreader 类

    public class Docreader {

    public String sentences[][]=new String[5][100];
    public String doc[]=new String[5];

    public Docreader() throws IOException{

    this.readdoc();
    this.splittosentence();

    }

   public void readdoc() throws IOException {
        for (int i = 0; i < 5; i++) {
            String temp = new String();
            temp = Docreader.readFile("datatrain/doc" + (i + 1) + ".txt");
            this.doc[i] = temp;
        }

    }

    public void splittosentence() {


        for (int i = 0; i < 5; i++) {
            String temp[];
            temp = doc[i].split("\\.");
            for(int j=0;j<temp.length;j++){
            sentences[i][j]=temp[j];

            }

        }

    }

    private static String readFile(String fileName) throws IOException {
        try (BufferedReader br = new BufferedReader(new FileReader(fileName))) {
            StringBuilder sb = new StringBuilder();
            String line = br.readLine();

            while (line != null) {
                sb.append(line);
                sb.append("\n");
                line = br.readLine();
            }
            return sb.toString();
        }
    }
}

例外:

Exception in thread "main" java.lang.NullPointerException
at java.io.StringReader.<init>(StringReader.java:50)
at stki_d_8_final.STKI_D_8_Final.main(STKI_D_8_Final.java:45)

Java 结果:1

当我在StringReaderClass 中检查第 50 行时,它包含

this.length = s.length();
4

2 回答 2

4

在这部分代码中:

while (reader.sentences[i][j] != null) {
    System.out.println(reader.sentences[i][j]);
    j++;              
    String temp=reader.sentences[i][j];
    StringReader h = new StringReader(temp);
}

您正在使用j++所以值j增加 1,然后您有以下代码:

String temp=reader.sentences[i][j];

由于数组中的这个新条目如果与 不同,则尚未评估null,因此它可能包含一个null值,该值被分配给并因此用一个值作为参数来temp初始化。StringReadernull

j在使用它构建StringReader. 此外,在其当前形式中,ArrayIndexOutOfBoundsException如果所有值reader.sentences[i]都不是,则此代码也可能抛出null。这将是上述代码的解决方案:

while (j < reader.sentences[i].length && reader.sentences[i][j] != null) {
    System.out.println(reader.sentences[i][j]);
    String temp=reader.sentences[i][j];
    StringReader h = new StringReader(temp);
    j++;
}
于 2015-01-05T03:05:41.447 回答
3

在这部分代码中:

while (reader.sentences[i][j] != null) {
        System.out.println(reader.sentences[i][j]);
        j++;              
        String temp=reader.sentences[i][j];
        StringReader h = new StringReader(temp);
}

您适当地确保 ,reader.sentences[i][j] != null然后您增加 j ( j++) 并且进行空检查。

于 2015-01-05T03:06:46.387 回答