1. AbortPolicy（默认策略）
特点：当任务无法被线程池执行时，会抛出一个RejectedExecutionException异常。
使用场景：适用于对任务丢失敏感的场景，当线程池无法接受新任务时，希望立即知道并处理该异常。
示例代码：
import java.util.concurrent.*;
public class AbortPolicyDemo {
public static void main(String[] args) {
ThreadPoolExecutor executor = new ThreadPoolExecutor(
2, 2, 0L, TimeUnit.MILLISECONDS,
new LinkedBlockingQueue<>(2),
new ThreadPoolExecutor.AbortPolicy());
for (int i = 0; i < 5; i++) {
executor.submit(() -> {
System.out.println("Task " + Thread.currentThread().getName() + " is running.");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
});
}
executor.shutdown();
}
}
2. CallerRunsPolicy
特点：当任务无法被线程池执行时，会直接在调用者线程中运行这个任务。如果调用者线程正在执行一个任务，则会创建一个新线程来执行被拒绝的任务。
使用场景：适用于可以容忍任务在调用者线程中执行的业务场景，它允许任务继续执行，而不会因为线程池资源不足而被丢弃。
示例代码：
import java.util.concurrent.*;
public class CallerRunsPolicyDemo {
public static void main(String[] args) {
ThreadPoolExecutor executor = new ThreadPoolExecutor(
2, 2, 0L, TimeUnit.MILLISECONDS,
new LinkedBlockingQueue<>(2),
new ThreadPoolExecutor.CallerRunsPolicy());
for (int i = 0; i < 5; i++) {
executor.submit(() -> {
System.out.println("Task " + Thread.currentThread().getName() + " is running.");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
});
}
executor.shutdown();
}
}
3. DiscardPolicy
特点：当任务无法被线程池执行时，任务将被直接丢弃，不抛出异常，也不执行任务。
使用场景：适用于对任务丢失不敏感的场景，当线程池无法接受新任务时，简单地丢弃被拒绝的任务。
示例代码：
import java.util.concurrent.*;
public class DiscardPolicyDemo {
public static void main(String[] args) {
ThreadPoolExecutor executor = new ThreadPoolExecutor(
2, 2, 0L, TimeUnit.MILLISECONDS,
new LinkedBlockingQueue<>(2),
new ThreadPoolExecutor.DiscardPolicy());
for (int i = 0; i < 5; i++) {
executor.submit(() -> {
System.out.println("Task " + Thread.currentThread().getName() + " is running.");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
});
}
executor.shutdown();
}
}