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我知道这个问题很常见，所以我一直在网上疯狂地寻找解决方案，但无济于事。我只是想从程序 JAR 中加载一个包含一些文本的文件。这是我试图阅读的内容：

            String text = "";
            int read, N = 1024 * 1024;
            char[] buffer = new char[N];
            try {

                InputStream is = this.getClass().getClassLoader().getResourceAsStream("/help.txt");
                BufferedReader br = new BufferedReader(new InputStreamReader(is));
                while(true) {
                    read = br.read(buffer, 0, N);
                    text += new String(buffer, 0, read);
                    if(read < N) {
                        break;
                    }
                }
            } catch(Exception ex) {
                ex.printStackTrace();
            }

我不太了解 java/eclipse 构建路径的东西。但我已将 help.txt 放在项目文件夹的根目录中。我目前在执行上面的代码时收到此错误。

java.lang.NullPointerException
    at java.io.Reader.<init>(Reader.java:78)
    at java.io.InputStreamReader.<init>(InputStreamReader.java:72)
    at ajax.Gui.printHelp(Gui.java:330)
    at ajax.Gui.onCommand(Gui.java:151)
    at ajax.Gui$1.actionPerformed(Gui.java:130)
    at javax.swing.JTextField.fireActionPerformed(JTextField.java:508)
    at javax.swing.JTextField.postActionEvent(JTextField.java:721)
    at javax.swing.JTextField$NotifyAction.actionPerformed(JTextField.java:836)
    at javax.swing.SwingUtilities.notifyAction(SwingUtilities.java:1661)
    at javax.swing.JComponent.processKeyBinding(JComponent.java:2870)
    at javax.swing.JComponent.processKeyBindings(JComponent.java:2917)
    at javax.swing.JComponent.processKeyEvent(JComponent.java:2833)
    at java.awt.Component.processEvent(Component.java:6282)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4861)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.java:1895)
    at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboardFocusManager.java:762)
    at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeyboardFocusManager.java:1027)
    at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeyboardFocusManager.java:899)
    at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:727)
    at java.awt.Component.dispatchEventImpl(Component.java:4731)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Window.dispatchEventImpl(Window.java:2719)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:729)
    at java.awt.EventQueue.access$200(EventQueue.java:103)
    at java.awt.EventQueue$3.run(EventQueue.java:688)
    at java.awt.EventQueue$3.run(EventQueue.java:686)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:702)
    at java.awt.EventQueue$4.run(EventQueue.java:700)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:699)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

做什么？一些额外信息：操作系统 = Linux Mint 14 KDE，JDK = JavaSE1.7，IDE = Eclipse

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2 回答 2

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您可以尝试不使用“/”

InputStream 是 = this.getClass().getClassLoader().getResourceAsStream("help.txt");

如果您在根目录中添加了文件，这应该可以工作。

或者您可以使用绝对文件路径创建 URL，然后使用

InputStream is = url.openStream();
于 2013-04-23T17:55:24.213 回答
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该方法getResourceAsStream正在返回null，因为它找不到文件。

您可以执行以下操作之一：

  • 确保文件在类路径中；这就是getResourceAsStream搜索的地方。
  • 将文件放在一个resources目录中，如本例所示。
  • 或者您可以将它放在源目录结构中，就像在这个 stackoverflow 问题中一样。

此外，您可能希望使用 aStringBuilder来构建您的字符串，而不是在String之后连接String。

于 2013-04-23T17:56:13.453 回答