Java不释放内存

Question

我有一个守护程序，它读取文件的内容，然后将其压缩并将其写入较小的 .tar.gz 文件。

出于某种原因，Java 会继续分配内存，即使在我释放(或者我认为我已经释放)所有已用内存之后也是如此。我的代码/推理有什么问题？

FileOutputStream fos    = null;
GZIPOutputStream gzipos = null;
OutputStreamWriter osw  = null;

BufferedWriter bw = null;
while (true) {
    if (f.length() != 0) {
        if (outputfile == null) {
            outputfile = outputfileroot + "_" + outputPart + ".tar.gz";

            fos = new FileOutputStream(outputfile);
            gzipos  = new GZIPOutputStream(fos);
            osw = new OutputStreamWriter(gzipos);
            bw  = new BufferedWriter(osw);
        }
        else if (new File(outputfile).length() > maxLengthOutputFile) {
            bw.flush();
            osw.flush();
            gzipos.flush();
            fos.flush();
            bw.close();
            osw.close();
            gzipos.close();
            fos.close();

            bw  = null;
            osw = null;
            gzipos  = null;
            fos = null;

            System.gc();

            System.out.println("Finished writing " + outputfileroot + "_" + outputPart + ".tar.gz");

            outputfile = outputfileroot + "_" + ++outputPart + ".tar.gz";
            fos     = new FileOutputStream(outputfile);
            gzipos  = new GZIPOutputStream(fos);
            osw     = new OutputStreamWriter(gzipos);
            bw      = new BufferedWriter(osw);
        }

        /**
         * Read the entire file
         */
        BufferedReader br = new BufferedReader(new FileReader(f));
        String line;
        while ((line = br.readLine()) != null) {
            // will send the content to another thread, so I need to read it line by line
            bw.write(line + "\r\n");
        }
        br.close();
        br = null;
        bw.flush();

        /**
         * Empty it
         */
        FileWriter fw = new FileWriter(f);
        fw.write("");
        fw.flush();
        fw.close();
        fw = null;
    }

    Thread.sleep(1000);
}

Answer 1

你把这个煮过头了。所有这些 null 设置和 gc() 调用实际上并没有帮助，而且您的刷新和关闭次数是您真正需要的数倍。此外，您根本不需要使用 Readers 和 Writers。所有这些都可以简化为:

GZIPOutputStream gzipos = null;
while (true)
{
    if (f.length() != 0)
    {
        if (outputfile == null)
        {
            outputfile = outputfileroot + "_" + outputPart + ".tar.gz";
            gzipos = new GZIPOutputStream(new FileOutputStream(outputfile));
        }
        else
        {
            if (new File(outputfile).length() > maxLengthOutputFile)
            {
                gzipos.close();
                System.out.println("Finished writing " + outputfileroot + "_" + outputPart + ".tar.gz");
                outputfile = outputfileroot + "_" + ++outputPart + ".tar.gz";
                gzipos = new GZIPOutputStream(new FileOutputStream(outputfile));
            }
        }

        /**
         * Read the entire file
         */
        InputStream in = new FileInputStream(f);
        byte[] buffer = new byte[8192];
        int count;
        while ((count = in.read(buffer)) > 0)
        {
            gzipos.write(buffer, 0, count);
        }
        in.close();
        gzipos.flush();
        /**
         * Empty it
         */
        f.createNewFile();
    }
    Thread.sleep(1000);
}

我无法理解你的评论“将把内容发送到另一个线程，所以我需要逐行阅读它”。此代码中没有线程，您不需要逐行输入。

我也很好奇它如何与生成输入文件的任何内容交互。我认为您应该在决定复制输入文件后立即重命名输入文件，并在其位置创建一个新的空文件，而不是在复制步骤之后。