Java . util . concurrent . exchange 类，带示例
原文:https://www . geesforgeks . org/Java-util-concurrent-exchange-class-with-examples/
交换器是 Java 最有意思的同步类。它通过创建一个同步点，方便了一对线程之间的元素交换。它简化了两个线程之间的数据交换。它的操作很简单:只需等待两个独立的线程调用它的 exchange() 方法。当这种情况发生时，它交换线程提供的数据。也可以看作是双向同步队列。它是一个泛型类，声明如下。
类语法:
Exchanger<V>
这里，V 指定正在交换的数据类型。
等级体系
java.lang.Object
↳ java.util.concurrent.Exchanger<V>
构造函数:
- [switch ()] –Create a new switch object with default values for its members.
方法:
-
交换(V x)–当调用此函数时，会导致当前线程暂停其执行，并等待另一个线程调用其交换方法。当另一个线程调用它的交换方法时，线程交换它们的数据，执行继续。
语法:
```java public V exchange(V x) throws InterruptedException
```
-
交换(V x，长超时，time unit unit)–当调用此函数时，会导致当前线程暂停其执行，等待另一个线程调用其交换方法。当另一个线程调用它的交换方法时，线程交换它们的数据，执行继续。线程只等待超时参数指定的持续时间，如果超时持续时间已过，将引发超时异常。
语法:
```java public V exchange(V x, long timeout, TimeUnit unit) throws InterruptedException, TimeoutException
```
示例演示交换机类的工作:
import java.util.concurrent.Exchanger;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
public class ExchangerDemo {
public static void main(String[] args)
{
Exchanger<String> exchanger = new Exchanger<>();
new UseString(exchanger);
new MakeString(exchanger);
}
}
// A thread that makes a string
class MakeString implements Runnable {
Exchanger<String> ex;
String str;
MakeString(Exchanger<String> ex)
{
this.ex = ex;
str = new String();
new Thread(this).start();
}
public void run()
{
char ch = 'A';
try {
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 5; j++) {
str += ch++;
}
if (i == 2) {
// Exchange the buffer and
// only wait for 250 milliseconds
str
= ex.exchange(str,
250,
TimeUnit.MILLISECONDS);
continue;
}
// Exchange a full buffer for an empty one
str = ex.exchange(str);
}
}
catch (InterruptedException e) {
System.out.println(e);
}
catch (TimeoutException t) {
System.out.println("Timeout Occurred");
}
}
}
// A thread that uses a string
class UseString implements Runnable {
Exchanger<String> ex;
String str;
UseString(Exchanger<String> ex)
{
this.ex = ex;
new Thread(this).start();
}
public void run()
{
try {
for (int i = 0; i < 3; i++) {
if (i == 2) {
// Thread sleeps for 500 milliseconds
// causing timeout
Thread.sleep(500);
continue;
}
// Exchange an empty buffer for a full one
str = ex.exchange(new String());
System.out.println("Got: " + str);
}
}
catch (InterruptedException e) {
System.out.println(e);
}
}
}
输出:
Got: ABCDE
Got: FGHIJ
Timeout Occurred
参考:https://docs . Oracle . com/javase/7/docs/API/Java/util/concurrent/exchange . html
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