通过jvisualvm监控fullgc

jvisualvm添加visualgc插件，查看内容的状态转移

默认新生代:老生代比例为1:2,默认eden区和s1,s2区的比例为 8:1:1,通过设置很小的jvm堆参数，比如9M，这样新生代为3M，老生代为6M

设置一个对象为1M，并且不释放内容，可以很快看到内存的走向，从eden区转向s1,再移到old区，经过几次之后old区也满了，就产生fullgc，接着oom

public class Visual {

    byte[] bytes = new byte[1024 * 1024 * 1];

    public static void main(String[] args) throws InterruptedException {
        case2();
    }

    private static void case1() throws InterruptedException {
        List<Visual> list = new ArrayList<>();
        for (; ; ) {
            list.add(new Visual());
            System.out.println(new Date().toString());
            Thread.sleep(100L);
        }
    }

    private static void case2() throws InterruptedException {
        List<Visual> list = new ArrayList<>();
        for (; ; ) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    for (int i = 0; i < 1000; i++) {
                        list.add(new Visual());
                        try {
                            Thread.sleep(100L);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }).start();

            Thread.sleep(10000L);
        }
    }
}