测试 synchronized（升级，申请总线锁） 对Long 做++操作 和 AtomicLong（CAS实现） LongAddr（分段+CAS实现）
先说结论
高并发情况下，LongAddr 优于 Atomic 优于 Synchronized
public class AtomicLearn {private static long count;private static AtomicLong count1=new AtomicLong(0);private static LongAdder count2=new LongAdder();@SneakyThrowspublic static void main(String[] args) {Thread[] threads=new Thread[1000];for(int i=0;i< threads.length;i++){threads[i]=new Thread(()->{for(int k=0;k<100000;k++){count1.getAndIncrement();}});}long start =System.currentTimeMillis();for (Thread t:threads) t.start();for (Thread t:threads) t.join();System.out.println("Atomic count1="+count1+" 用时："+(System.currentTimeMillis()-start));
//-- longAddrThread[] threads2=new Thread[1000];for(int i=0;i< threads2.length;i++){threads2[i]=new Thread(()->{for(int k=0;k<100000;k++){count2.increment();}});}long start2 =System.currentTimeMillis();for(Thread t:threads2) t.start();for(Thread t:threads2) t.join();System.out.println("LongAddr count2="+count2+" 用时："+(System.currentTimeMillis()-start2));// ---- synchronizedThread[] threads0=new Thread[1000];for(int i=0;i< threads0.length;i++){threads0[i]=new Thread(()->{for(int k=0;k<100000;k++){synchronized(AtomicLearn.class){count++;}}});}long start0 =System.currentTimeMillis();for(Thread t:threads0) t.start();for(Thread t:threads0) t.join();System.out.println("synchronized count1="+count+" 用时："+(System.currentTimeMillis()-start0));}}