1、AtomicReference用以支援對象的原子操作：AtomicReference 可以封裝引用一個V執行個體。
2、public final boolean compareAndSet(V expect, V update) ，可以支援并發通路，set的時候進行對比判斷，如果目前值和操作之前一樣則傳回false，否則表示資料沒有變化。
執行個體代碼：package com.what21;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicReference;
public class AtomicReferenceMain {
private static AtomicReference ar = new AtomicReference(0);
public static void test() throws InterruptedException {
int t = 100;
final int c = 100;
final CountDownLatch latch = new CountDownLatch(t);
for (int i = 0; i
new Thread(new Runnable() {
@Override
public void run() {
for (int i = 0; i
while (true) {
Integer temp = ar.get();
System.out.println("temp=" + temp);
if (ar.compareAndSet(temp, temp + 1)) {
break;
}
}
}
latch.countDown();
}
}).start();
}
latch.await();
System.out.println(ar.get());
}
public static void main(String[] args) throws InterruptedException {
test();
}
}
執行個體代碼，原子量實作的計數器：package com.what21;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicInteger;
public class AtomicCounter {
private AtomicInteger value = new AtomicInteger();
public int getValue() {
return value.get();
}
public int increase() {
return value.incrementAndGet();// 内部使用死循環for(;;)調用compareAndSet(current, next)
// return value.getAndIncrement();
}
public int increase(int i) {
return value.addAndGet(i);// 内部使用死循環for(;;)調用compareAndSet(current, next)
// return value.getAndAdd(i);
}
public int decrease() {
return value.decrementAndGet();// 内部使用死循環for(;;)調用compareAndSet(current, next)
// return value.getAndDecrement();
}
public int decrease(int i) {
return value.addAndGet(-i);// 内部使用死循環for(;;)調用compareAndSet(current, next)
// return value.addAndGet(-i);
}
public static void main(String[] args) {
final AtomicCounter counter = new AtomicCounter();
ExecutorService service = Executors.newCachedThreadPool();
for (int i = 0; i
service.execute(new Runnable() {
@Override
public void run() {
System.out.println(counter.increase());
}
});
}
service.shutdown();
}
}
執行個體代碼，原子量實作的銀行取款：package com.what21;
import java.util.Random;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicLong;
public class AtomicAccount {
private AtomicLong balance;
public AtomicAccount(long money) {
balance = new AtomicLong(money);
System.out.println("Total Money:" + balance);
}
public void deposit(long money) {
balance.addAndGet(money);
}
public void withdraw(long money) {
for (; ; ) {//保證即時同一時間有人也在取款也可以再次嘗試取款，如果不需要并發嘗試取款，可以去掉這句
long oldValue = balance.get();
if (oldValue
System.out.println(Thread.currentThread().getName() + " 餘額不足！ 餘額：" + balance);
break;
}
try {Thread.sleep(new Random().nextInt(1000));} catch (Exception e) { }// 模拟取款時間
if (balance.compareAndSet(oldValue, oldValue - money)) {
System.out.println(Thread.currentThread().getName() + " 取款 " + money + " 成功！ 餘額：" + balance);
break;
}
System.out.println(Thread.currentThread().getName() + " 遇到并發，再次嘗試取款！");
}
}
public static void main(String[] args) {
final AtomicAccount account = new AtomicAccount(1000);
ExecutorService pool = Executors.newCachedThreadPool();
int i = 0;
while (i++
pool.execute(new Runnable() {
@Override
public void run() {
account.withdraw(100);
}
});
}
pool.shutdown();
}
}