将src文件夹中的文件加载到阅读器中

Question

我想知道我怎么可以将文件加载lol.txt从src文件夹到我的close方法。到目前为止的代码：

              public void close() throws IOException {
        boolean loadFromClasspath = true;
        String fileName = "..."; // provide an absolute path here to be sure that file is found
        BufferedReader reader = null;
        try {

            if (loadFromClasspath) {
                // loading from classpath
                // see the link above for more options
                InputStream in = getClass().getClassLoader().getResourceAsStream("lol.txt"); 
                reader = new BufferedReader(new InputStreamReader(in));
            } else {
                // load from file system
                reader = new BufferedReader(new FileReader(new File(fileName)));
            }

            String line = null;
            while ( (line = reader.readLine()) != null) {
                // do something with the line here
                System.out.println("Line read: " + line);
            }
        } catch (IOException e) {
            JOptionPane.showMessageDialog(null,e.getMessage()+" for lol.txt","File Error",JOptionPane.ERROR_MESSAGE);
        } finally {
            if (reader != null) {
                reader.close();  
            }
        }
    }

启动时控制台错误输出：

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at java.io.Reader.<init>(Unknown Source)
at java.io.InputStreamReader.<init>(Unknown Source)
at main.main.close(main.java:191)
at main.main$1.windowClosing(main.java:24)
at java.awt.Window.processWindowEvent(Unknown Source)
at javax.swing.JFrame.processWindowEvent(Unknown Source)
at java.awt.Window.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$000(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

Answer 1

如果您想从jar文件中加载文件（例如，从classpath加载），请参阅此答案以获取有关如何获取的更多选项InputStream。在下面的代码中，我没有进行任何异常处理，并删除了您的Random相关代码。

public void close() {
    boolean loadFromClasspath = true;
    String fileName = "..."; // provide an absolute path here to be sure that file is found
    BufferedReader reader = null;
    try {

        if (loadFromClasspath) {
            // loading from classpath
            // see the link above for more options
            InputStream in = getClass().getClassLoader().getResourceAsStream("absolute/path/to/file/inside/jar/lol.txt"); 
            reader = new BufferedReader(new InputStreamReader(in));
        } else {
            // load from file system
            reader = new BufferedReader(new FileReader(new File(fileName)));
        }

        String line = null;
        while ( (line = reader.readLine()) != null) {
            // do something with the line here
            System.out.println("Line read: " + line);
        }
    } catch (IOException e) {
        JOptionPane.showMessageDialog(null,e.getMessage()+" for lol.txt","File Error",JOptionPane.ERROR_MESSAGE);
    } finally {
        if (reader != null) {
            reader.close();  
        }
    }
}

编辑：
似乎您在文件夹结构上做错了什么，或者您使用了错误的包/文件名。只是要清楚。目前，您似乎main在一个main程序包下有一个叫做的类。您的文件夹结构应如下所示：

+ src/
   + main/
      main.java
      lol.txt

编译时，应将您的lol.txt文件（顺便说一下，它们是小写的 L， 不是数字 1 正确吗？）应复制到/bin/main/文件夹下

如果是这种情况，请使用如下代码： InputStream in = getClass().getClassLoader().getResourceAsStream("main/lol.txt");

如果您的文件夹结构不同，请进行相应的更改