线程“Thread-9”java.lang.OutOfMemoryError 中的异常：Java 堆空间

Question

我一直在为我的游戏编写更新程序。

1. 它会检查 drop box 上的 .version 文件并将其与本地 .version 文件进行比较。

2. 如果本地版本的文件中缺少任何链接，它会一一下载所需的链接。

这是它显示的错误

Exception in thread "Thread-9" java.lang.OutOfMemoryError: Java heap space
at com.fox.listeners.ButtonListener.readFile(ButtonListener.java:209)
at com.fox.listeners.ButtonListener.readFile(ButtonListener.java:204)
at com.fox.listeners.ButtonListener.UpdateStart(ButtonListener.java:132)
at com.fox.listeners.ButtonListener$1.run(ButtonListener.java:58)

它只显示某些计算机，但并非所有计算机都是 readFile 方法

private byte[] readFile(URL u) throws IOException {
    return readFile(u, getFileSize(u));
}

private static byte[] readFile(URL u, int size) throws IOException {
    byte[] data = new byte[size];
    int index = 0, read = 0;
    try {
        HttpURLConnection conn = null;
        conn = (HttpURLConnection) u.openConnection();
        conn.addRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)");
        InputStream is = conn.getInputStream();
        progress_a = 0;
        progress_b = data.length;
        while(index < data.length) {
            read = is.read(data, index, size-index);
            index += read;
            progress_a = index;
        }
    } catch(Exception e) {
        e.printStackTrace();
    }

    return data;
}

private byte[] readFile(File f) {
    byte[] data = null;
    try {
        data = new byte[(int)f.length()];

        @SuppressWarnings("resource")
        DataInputStream dis = new DataInputStream(new FileInputStream(f));
        dis.readFully(data);
    } catch (IOException e) {
        e.printStackTrace();
    }
    return data;
}

这是运行的主要方法

public void UpdateStart() {
    System.out.println("Starting Updater..");

    if(new File(cache_dir).exists() == false) {
        System.out.print("Creating cache dir.. ");
        while(new File(cache_dir).mkdir() == false);
        System.out.println("Done");
    }


    try {
        version_live = new Version(new URL(version_file_live));
    } catch(MalformedURLException e) {
        e.printStackTrace();
    }

    version_local = new Version(new File(version_file_local));

    Version updates = version_live.differences(version_local);

    System.out.println("Updated");

    int i = 1;
    try {
        byte[] b = null, data = null;
        FileOutputStream fos = null;
        BufferedWriter bw = null;


        for(String s : updates.files) {
            if(s.equals(""))
                continue;


            System.out.println("Reading file "+s);
            AppFrame.pbar.setString("Downloading file "+ i + " of "+updates.files.size());
            if(progress_b > 0) {
                s = s + " " +(progress_a * 1000L / progress_b / 10.0)+"%";
            }

            b = readFile(new URL(s));



            progress_a = 0;
            progress_b = b.length;

            AppFrame.pbar.setString("Unzipping file "+ i++ +" of "+updates.files.size());

            ZipInputStream zipStream = new ZipInputStream(new ByteArrayInputStream(b));
            File f = null, parent = null;
            ZipEntry entry = null;
            int read = 0, entry_read = 0;
            long entry_size = 0;
            progress_b = 0;

            while((entry = zipStream.getNextEntry()) != null)
                progress_b += entry.getSize();

            zipStream = new ZipInputStream(new ByteArrayInputStream(b));

            while((entry = zipStream.getNextEntry()) != null) {
                f = new File(cache_dir+entry.getName());
                if(entry.isDirectory())
                    continue;

                System.out.println("Making file "+f.toString());

                parent = f.getParentFile();
                if(parent != null && !parent.exists()) {
                    System.out.println("Trying to create directory "+parent.getAbsolutePath());
                    while(parent.mkdirs() == false);
                }

                entry_read = 0;
                entry_size = entry.getSize();
                data = new byte[1024];
                fos = new FileOutputStream(f);

                while(entry_read < entry_size) {
                    read = zipStream.read(data, 0, (int)Math.min(1024, entry_size-entry_read));
                    entry_read += read;
                    progress_a += read;
                    fos.write(data, 0, read);
                }
                fos.close();
            }

            bw = new BufferedWriter(new FileWriter(new File(version_file_local), true));
            bw.write(s);
            bw.newLine();
            bw.close();
        }
    } catch(Exception e) {
        e.printStackTrace();
        return;
    }

    System.out.println(version_live);
    System.out.println(version_local);
    System.out.println(updates);
    CacheUpdated = true;
    if(CacheUpdated) {
        AppFrame.pbar.setString("All Files are downloaded click Launch to play!");
    }

}

我不明白为什么它对我的一些玩家有效，而对我的其他一些玩家却无效唯一需要我解决的大问题。

Answer 1

要么增加分配给 JVM 的内存 (How can I increase the JVM memory?)，要么确保加载到内存中的文件不是很大（如果是，你需要找到替代解决方案，或者只是读取块一次加载而不是将整个内容加载到内存中）。

Answer 2

分几个步骤进行更新。这是 Java 8 的一些伪代码。它比您编写的要短得多，因为 Java 有很多内置工具，您重写的效率要低得多。

// Download
Path zipDestination = Paths.get(...);
try (InputStream  in = source.openStream()) {
  Files.copy(in, zipDestination);
}

// Unzip
try (ZipFile zipFile = new ZipFile(zipDestination.toFile())) {
  for (ZipEntry e: Collections.list(zipFile.entries())) {
    Path entryDestination = Paths.get(...);
    Files.copy(zipFile.getInputStream(e), entryDestination);
  }
}

// Done.