使用计算机时Java垃圾回收会增加吗？

Question

我正在运行String vs StringBuilder测试来探索Java GC以及JIT。

我注意到了一些奇怪的东西。此图，从0分钟到2:31 AM，除了我的Java程序外，我的计算机基本上什么也不做：

然后我开始四处游荡，打开游戏，浏览网页，然后突然垃圾回收变得更具攻击性：（大约2:35 AM）

让我们再次使用Thread.sleep（1000）运行测试：

这对我来说毫无意义。看一下他在前2个图中分配了Heap ...没有变化。 JVM是否检测到它的堆空间可能受到攻击？当我查看CPU时，其使用率保持在25％或更少，因此没有CPU瓶颈。 然后在第三张图中，它与我在玩游戏而不是在玩游戏时完全相同地分配堆（使用CPU是我要在此处说明的要点）。

为什么会这样？

代码可能有所作为：

public static void main(String[] args) throws IOException, InterruptedException {

        GCTests test = new GCTests();


        // Test setup
        int iterations = 1000;   // with 800MB


        // Keep running so I can see the results in jvisualm
        while(true) {



            System.out.println("\n\n\n\n\nSTARTING STRING TEST");
            test.withString(iterations);
            System.out.println("\n\n\n\n\nALL DONE STRING TEST");
            Thread.sleep(20000);



            System.out.println("\n\n\n\n\nSTARTING STRINGBUILDER TEST");
            test.withStringBuilder(iterations);
            System.out.println("\n\n\n\n\nALL DONE STRINGBUILDER TEST");
            Thread.sleep(20000);

        }

    }


    public void withString(int iterations) throws IOException, InterruptedException{

        // Connect scanner to file
        File file = new File("C:\\Users\\userx\\Desktop\\Intellij\\Practice\\DragNDrop\\src\\TextDragNDrop\\wordlist.10000.txt");
        Scanner in;



        // Append processed data to StringBuilder
        StringBuilder collectForOuput = new StringBuilder();
        String inputStr = "";   // Allow every line to consume one string


        //////// START iterationsIndex times loop ////////////
        // Trying to get millions of Strings being made
        int iterationsIndex = 0;
        while(iterationsIndex < iterations) {





            ///////// START FILE ///////////////////
            in = new Scanner(file);

            // Number of lines to expect and an index for each line
            int wordsCount = 10000;
            int wordCountIndex = 0;

            //in.nextLine();  // Consume newline

            while (wordCountIndex < wordsCount) {

                inputStr = in.nextLine();  // Assign to string, newline is consumed so need to do another
                // nextLine()

                for (int i = 0; i < inputStr.length(); i += 2) {

                    collectForOuput.append(inputStr.charAt(i));
                }
                collectForOuput.append(" ");
                for (int i = 1; i < inputStr.length(); i += 2) {

                    collectForOuput.append(inputStr.charAt(i));
                }
                collectForOuput.append("\n");

                wordCountIndex++;
            }
            //////// END FILE ///////////////////////////



            ////////////////////////
            // TEST PAUSE FOR GC ///
            ////////////////////////
            //Thread.sleep(1000);



            // File processed. Report and start again.
            iterationsIndex++;
            //System.out.println(iterationsIndex + " iterations complete.");

        }//////// END iterationsIndex times loop ////////////


        // At 1_000 iterations
        //System.out.println(collectForOuput.toString());

    }


    public void withStringBuilder(int iterations) throws IOException, InterruptedException{

        // Connect scanner to file
        File file = new File("C:\\Users\\userx\\Desktop\\Intellij\\Practice\\DragNDrop\\src\\TextDragNDrop\\wordlist.10000.txt");
        Scanner in;



        // Append processed data to StringBuilder
        StringBuilder collectForOuput = new StringBuilder();
        StringBuilder inputStr = new StringBuilder();    // Every line is appended to
                                                        // SB and SB is made length 0
                                                        // after every line is processes...


        //////// START iterationsIndex times loop ////////////
        // Trying to get millions of Strings being made
        int iterationsIndex = 0;
        while(iterationsIndex<iterations) {





            ///////// START FILE ///////////////////
            in = new Scanner(file);

            // Number of lines to expect and an index for each line
            int wordsCount = 10000;
            int wordCountIndex = 0;

            //in.nextLine();  // Consume newline

            while (wordCountIndex < wordsCount) {

                // Append to StringBuilder, newline is consumed so need to do another
                // nextLine()
                inputStr.append(in.nextLine());

                for (int i = 0; i < inputStr.length(); i += 2) {

                    collectForOuput.append(inputStr.charAt(i));
                }
                collectForOuput.append(" ");
                for (int i = 1; i < inputStr.length(); i += 2) {

                    collectForOuput.append(inputStr.charAt(i));
                }
                collectForOuput.append("\n");
                inputStr.setLength(0);

                wordCountIndex++;
            }
            //////// END FILE ///////////////////////////



            ////////////////////////
            // TEST PAUSE FOR GC ///
            ////////////////////////
            //Thread.sleep(1000);



            // File processed. Report and start again.
            iterationsIndex++;
            //System.out.println(iterationsIndex + " iterations complete.");

        }//////// END iterationsIndex times loop ////////////


        // At 1_000 iterations
        //System.out.println(collectForOuput.toString());

    }