java中使用线程,核心走ThreadPooLExecutor
Executor封装好了四种线程池类
1.newCachedThreadPool创建一个可缓存线程池,如果线程池长度超过处理需要,可灵活回收空闲线程,若无可回收,则新建线程。
package threadpool;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class demo1 {
public static void main(String[] args) {
ExecutorService threadpool = Executors.newCachedThreadPool();
for (int i = 0; i < 100; i++) {
int temp=i;
threadpool.execute(new Runnable() {
public void run() {
System.out.println("线程名"+Thread.currentThread().getName() +",i:"+ temp);
}
});
}
}
}
执行结果,可以发现线程名很多都是有重复的。
2.newFixedThreadPool 创建一个定长线程池,支持定时及周期性任务执行。
package threadpool;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class demo1 {
public static void main(String[] args) {
// 设置最大线程数量
ExecutorService threadpool = Executors.newFixedThreadPool(3);
for (int i = 0; i < 10; i++) {
int temp = i;
threadpool.execute(new Runnable() {
public void run() {
System.out.println("线程名" + Thread.currentThread().getName() + ",i:" + temp);
}
});
}
}
}
运行结果,发现最大的线程数为3
3.newScheduledThreadPool 创建一个定长线程池,支持定时及周期性任务执行
package threadpool;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
ScheduledExecutorService threadpool = Executors.newScheduledThreadPool(3);
for (int i = 0; i < 10; i++) {
int temp = i;
threadpool.schedule(new Runnable() {
public void run() {
System.out.println("线程名" + Thread.currentThread().getName() + ",i:" + temp);
}
}, 3,TimeUnit.SECONDS);
}
}
}
3秒后执行线程,展示不了效果
4.newSingleThreadExecutor 创建一个单线程化的线程池,它只会用唯一的工作线程来执行任务,保证所有任务按照指定顺序执行。
package threadpool;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class demo1 {
public static void main(String[] args) {
ExecutorService threadpool = Executors.newSingleThreadExecutor();
for (int i = 0; i < 10; i++) {
int temp = i;
threadpool.execute(new Runnable() {
public void run() {
System.out.println("线程名" + Thread.currentThread().getName() + ",i:" + temp);
}
});
}
}
}
执行结果
其实和单线程没什么差别,所有几乎不太会用这个。