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;
 }
}