java - 并发修改异常

Question

下面的方法是从 AsynTask 的不同地方调用的。它是为 Android 编码的。获取 ConcurrentModificationException。如何使此方法线程安全

public static String saveJsonFile(File dir, String name, JSONObject data) {
        final File file = new File(dir.getPath() + File.separator + name);
        try {
            file.createNewFile();
        } catch (final IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }

        BufferedWriter printWriter = null;

        try {
            printWriter = new BufferedWriter(new FileWriter(file), 8192);
            // printWriter = new PrintWriter(file);
            if (data != null)
                data.write(printWriter); // java.util.ConcurrentModificationException



                      ........
                      ........

Answer 1

你可以这样做：

private final Object lock = new Object();

public static String saveJsonFile(File dir, String name, JSONObject data) {
    final File file = new File(dir.getPath() + File.separator + name);
    try {
        file.createNewFile();
    } catch (final IOException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }

    BufferedWriter printWriter = null;

    try {
        printWriter = new BufferedWriter(new FileWriter(file), 8192);

        synchronized(lock) {
            if (data != null)
                 data.write(printWriter); // java.util.ConcurrentModificationException
                 //...

Answer 2

synchronized使您的代码data：

synchronized(data) {
    try {
        printWriter = new BufferedWriter(new FileWriter(file), 8192);
        // ...
    }
}