JUC, java.util.concurrent并发工具包下。
1.原子整数
AtomicInteger
AtomicLong
AtomicBoolean
底层用的CAS来实现。
AtomicInteger类的incrementAndGet方法，addAndGet方法
public static void main(String[] args) {AtomicInteger atomicInteger = new AtomicInteger();int i = atomicInteger.incrementAndGet(); //i++log.info("i=={}", i);//这里返回的是1，但是atomicInteger中的值已经变成2了int j = atomicInteger.getAndIncrement();//++ilog.info("j=={}", j);log.info("value=={}", atomicInteger.get());//先返回原来的值int andAdd = atomicInteger.getAndAdd(2);log.info("andAdd={}", andAdd);//返回加运算之后的值int i1 = atomicInteger.addAndGet(3);log.info("i1=={}", i1);}int andAdd = atomicInteger.getAndAdd(-1 * 2); //减法
AtomicInteger类的updateAndGet方法的原理分析：
public final int updateAndGet(IntUnaryOperator updateFunction) {int prev, next;do {prev = get();next = updateFunction.applyAsInt(prev);} while (!compareAndSet(prev, next));return next;
}
IntUnaryOperator这个接口中定义了方法 int applyAsInt（int prev）,所以调用者只需要传入applyAsInt方法的实现逻辑即可。
AtomicInteger atomicInteger = new AtomicInteger(5);
//**乘法
int i2 = atomicInteger.updateAndGet(e -> e * 10);
log.info("i2=={}", i2);
2.原子引用类型
AtomicReference
AtomicMarkableReference
AtomicStampedReference
public class AccountDemo {public static void main(String[] args) {BigdecimalAccountCAS bigdecimalAccountCAS = new BigdecimalAccountCAS(new BigDecimal("10000"));BigDecimalAccount.demo(bigdecimalAccountCAS);}
}class BigdecimalAccountCAS implements BigDecimalAccount{private AtomicReference<BigDecimal> balance;public BigdecimalAccountCAS (BigDecimal balance) {this.balance = new AtomicReference<>(balance);}@Overridepublic BigDecimal getBalance() {return this.balance.get();}@Overridepublic void withDraw(BigDecimal amont) {while(true) {BigDecimal prev = balance.get();BigDecimal subtract = prev.subtract(amont);if (balance.compareAndSet(prev, subtract)) {break;}}
// this.balance.updateAndGet(e -> e.subtract(amont));}
}interface BigDecimalAccount {//获取余额BigDecimal getBalance();//取款void withDraw(BigDecimal amont);static void demo(BigDecimalAccount account) {//定义一个线程集合List<Thread> ts = new ArrayList<>();long start = System.nanoTime();//创建一千个线程，每个线程取出10元for (int i = 0; i < 1000; i++) {ts.add(new Thread(() -> account.withDraw(BigDecimal.TEN)));}//启动每一个线程ts.forEach( e -> e.start());//等所有线程执行完毕ts.forEach( e -> {try {e.join();} catch (InterruptedException e1) {e1.printStackTrace();}});long duration = System.nanoTime() - start;System.out.println("花费时长："+duration);System.out.println("余额："+ account.getBalance());}
}
