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import java.util.Random;

import java.util.concurrent.TimeUnit;

import java.util.concurrent.atomic.LongAdder;

/*

演示GC日志生成与解读

*/

public class GCLogAnalysis {

private static Random random = new Random();

public static void main(String[] args) {

// 当前毫秒时间戳

long startMillis = System.currentTimeMillis();

// 持续运行毫秒数; 可根据需要进行修改

long timeoutMillis = TimeUnit.SECONDS.toMillis(1);

// 结束时间戳

long endMillis = startMillis + timeoutMillis;

LongAdder counter = new LongAdder();

System.out.println("正在执行...");

// 缓存一部分对象; 进入老年代

int cacheSize = 2000;

Object[] cachedGarbage = new Object[cacheSize];

// 在此时间范围内,持续循环

while (System.currentTimeMillis() < endMillis) {

// 生成垃圾对象

Object garbage = generateGarbage(100*1024);

counter.increment();

int randomIndex = random.nextInt(2 * cacheSize);

if (randomIndex < cacheSize) {

cachedGarbage[randomIndex] = garbage;

}

}

System.out.println("执行结束!共生成对象次数:" + counter.longValue());

}

// 生成对象

private static Object generateGarbage(int max) {

int randomSize = random.nextInt(max);

int type = randomSize % 4;

Object result = null;

switch (type) {

case 0:

result = new int[randomSize];

break;

case 1:

result = new byte[randomSize];

break;

case 2:

result = new double[randomSize];

break;

default:

StringBuilder builder = new StringBuilder();

String randomString = "randomString-Anything";

while (builder.length() < randomSize) {

builder.append(randomString);

builder.append(max);

builder.append(randomSize);

}

result = builder.toString();

break;

}

return result;

}

}