如果AtomicReferenceArray对象的索引i处的当前值(称为见证值)等于期望值,则使用AtomicReferenceArray类的compareAndExchange()方法原子地将AtomicReferenceArray的索引i的值设置为newValue。此方法将返回见证值,该值将与期望值相同。此方法使用读取的内存语义来处理操作,就像将该变量声明为volatile一样。
用法:
public final boolean compareAndExchange( int i, E expectedValue, E newValue)
参数:此方法接受:
- i这是执行操作的AtomicReferenceArray的索引,
- expectedValue 这是期望值,
- newValue 这是要设置的新值。
返回值:此方法返回见证值,如果成功,它将与期望值相同。
以下示例程序旨在说明compareAndExchange()方法:
程序1:
// Java program to demonstrate
// compareAndExchange() method
import java.util.concurrent.atomic.*;
public class GFG {
public static void main(String[] args)
{
// create an atomic reference object.
AtomicReferenceArray<Integer> ref
= new AtomicReferenceArray<Integer>(3);
// set some value
ref.set(0, 1234);
ref.set(1, 4322);
// apply compareAndExchange()
int oldV1
= ref.compareAndExchange(0, 1234, 8913);
int oldV2
= ref.compareAndExchange(1, 4322, 6543);
// print
System.out.println("Old value at index 0:"
+ oldV1);
System.out.println("Old value at index 1:"
+ oldV2);
}
}
输出:
程序2:
// Java program to demonstrate
// compareAndExchange() method
import java.util.concurrent.atomic.*;
public class GFG {
public static void main(String[] args)
{
// create an atomic reference object.
AtomicReferenceArray<String> ref
= new AtomicReferenceArray<String>(3);
// set some value
ref.set(0, "GFG");
ref.set(1, "JS");
// apply compareAndExchange()
String oldV1
= ref.compareAndExchange(
0, "GFG",
"GEEKS FOR GEEKS");
String oldV2
= ref.compareAndExchange(
1, "JS",
"JAVA SCRIPT");
// print
System.out.println("Old value at index 0:"
+ oldV1);
System.out.println("New value at index 0:"
+ ref.get(0));
System.out.println("Old value at index 1:"
+ oldV2);
System.out.println("New value at index 1:"
+ ref.get(1));
}
}
输出:
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注:本文由纯净天空筛选整理自AmanSingh2210大神的英文原创作品 AtomicReferenceArray compareAndExchange() method in Java with Examples。非经特殊声明,原始代码版权归原作者所有,本译文未经允许或授权,请勿转载或复制。