package com.test;

import java.io.ByteArrayOutputStream;
import java.util.Arrays;
import java.util.List;
import java.util.stream.IntStream;

import com.google.common.collect.Lists;

/**
 * {@link https://blog.csdn.net/qq_42945742/article/details/84107531}
 * {@link https://blog.csdn.net/u011381576/article/details/79755069}
 * <pre>
 * javac -g:vars GcTest
 * javap -verbose GcTest
 * java -verbose:gc GcTest
 * </pre>
 * 
 * @author
 * @date 2021/01/20
 */
public class GcTest {
    public static void main(String[] args) {
        List<ByteArrayOutputStream> list = Lists.newArrayListWithCapacity(20);
        System.out.println("===");
        IntStream.range(0, 5).boxed().forEach(i -> {
            ByteArrayOutputStream bas = new ByteArrayOutputStream(64 * 1024 * 1024);
            list.add(bas);
            System.out.println("=====!\r\n");
        });
        System.out.println("===1");
        System.gc();
        System.out.println("===2");
        ByteArrayOutputStream[] basArray = list.stream().toArray(ByteArrayOutputStream[]::new);
        List<ByteArrayOutputStream> list2 = Arrays.asList(basArray);
        System.gc();
        System.out.println("===2");
        basArray = null;
        list.clear();
        System.gc();
        System.out.println("===3");
        list2 = null;
        System.gc();
        System.out.println("===4");

    }

    private static void test3() {
        {
            byte[] placeholder = new byte[64 * 1024 * 1024];
        }
        int a = 0;
        System.gc();
        System.out.println("====");
    }

    private static void test2() {
        {
            int b = 0;
            byte[] placeholder = new byte[64 * 1024 * 1024];
        }
        int a = 0;
        System.gc();
        System.out.println("====");
    }

    private static void test1() {
        {
            int b = 0;
            byte[] placeholder = new byte[64 * 1024 * 1024];
        }
        ByteArrayOutputStream bas = new ByteArrayOutputStream(64 * 1024 * 1024);
        for (int i = 0; i < 64 * 1024 * 1024; i++) {
            bas.write(i);
        }
        byte[] xx = bas.toByteArray();
        byte[] yy = Arrays.copyOf(xx, xx.length);
        System.out.println("====");
        int a = 0;
        System.gc();
        System.out.println("====");
        bas = null;
        System.gc();
        System.out.println("====");
        yy = null;
        System.gc();
        System.out.println("====");
        xx = null;
        System.gc();
        System.out.println("====");
    }
}