java.util.concurrent.atomic.AtomicReferenceArray类提供可以原子方式读取和写入的底层引用数组的操作,还包含高级原子操作. AtomicReferenceArray支持对底层引用数组变量的原子操作.它具有get和set方法,类似于对volatile变量的读写操作.也就是说,一个集合与之前的相关变量的任何后续获取具有先发生关系.原子compareAndSet方法也具有这些内存一致性功能.
以下是AtomicReferenceArray类中可用的重要方法列表.
Sr.No. | 方法&说明 |
---|---|
1 | public boolean compareAndSet(int i,E expect,E update) 如果当前值==期望值,则以原子方式将位置i的元素设置为给定的更新值. |
2 | public E get(int i) 获取位置i的当前值. |
3 | public E getAndSet(int i ,E newValue) 以原子方式将位置i的元素设置为给定值并返回旧值. |
4 | public void lazySet(int i, E newValue) 最终将位置i的元素设置为给定值. |
5 | public int length() 返回数组的长度. |
6 | public void set(int i,E newValue) 将位置i的元素设置为给定值. |
7 | public String toString() 返回数组当前值的String表示. |
8 | 公共布尔值weakCompareAndSet(int i,E expect,E update) 原子如果当前值==期望值,则将位置i处的元素设置为给定的更新值. |
以下TestThread程序显示在基于线程的环境中使用AtomicReferenceArray变量.
import java.util.concurrent.atomic.AtomicReferenceArray; public class TestThread { private static String[] source = new String[10]; private static AtomicReferenceArray<String> atomicReferenceArray = new AtomicReferenceArray<String>(source); public static void main(final String[] arguments) throws InterruptedException { for (int i = 0; i<atomicReferenceArray.length(); i++) { atomicReferenceArray.set(i, "item-2"); } Thread t1 = new Thread(new Increment()); Thread t2 = new Thread(new Compare()); t1.start(); t2.start(); t1.join(); t2.join(); } static class Increment implements Runnable { public void run() { for(int i = 0; i<atomicReferenceArray.length(); i++) { String add = atomicReferenceArray.getAndSet(i,"item-"+ (i+1)); System.out.println("Thread " + Thread.currentThread().getId() + ", index " +i + ", value: "+ add); } } } static class Compare implements Runnable { public void run() { for(int i = 0; i<atomicReferenceArray.length(); i++) { System.out.println("Thread " + Thread.currentThread().getId() + ", index " +i + ", value: "+ atomicReferenceArray.get(i)); boolean swapped = atomicReferenceArray.compareAndSet(i, "item-2", "updated-item-2"); System.out.println("Item swapped: " + swapped); if(swapped) { System.out.println("Thread " + Thread.currentThread().getId() + ", index " +i + ", updated-item-2"); } } } } }
这将产生以下结果.
Thread 9, index 0, value: item-2 Thread 10, index 0, value: item-1 Item swapped: false Thread 10, index 1, value: item-2 Item swapped: true Thread 9, index 1, value: updated-item-2 Thread 10, index 1, updated-item-2 Thread 10, index 2, value: item-3 Item swapped: false Thread 10, index 3, value: item-2 Item swapped: true Thread 10, index 3, updated-item-2 Thread 10, index 4, value: item-2 Item swapped: true Thread 10, index 4, updated-item-2 Thread 10, index 5, value: item-2 Item swapped: true Thread 10, index 5, updated-item-2 Thread 10, index 6, value: item-2 Thread 9, index 2, value: item-2 Item swapped: true Thread 9, index 3, value: updated-item-2 Thread 10, index 6, updated-item-2 Thread 10, index 7, value: item-2 Thread 9, index 4, value: updated-item-2 Item swapped: true Thread 9, index 5, value: updated-item-2 Thread 10, index 7, updated-item-2 Thread 9, index 6, value: updated-item-2 Thread 10, index 8, value: item-2 Thread 9, index 7, value: updated-item-2 Item swapped: true Thread 9, index 8, value: updated-item-2 Thread 10, index 8, updated-item-2 Thread 9, index 9, value: item-2 Thread 10, index 9, value: item-10 Item swapped: false