【Java】Java线程池ExecutorService中重要的方法

• Z时代
• 2024-01-10
• 分类：技术分享

1. ThreadPoolExecutor
2. ScheduledThreadPoolExecutor

ExecutorService executorService = Executors.newFixedThreadPool(10);
executorService.execute(new Runnable() {
public void run() {
System.out.println("入门小站");
}
});
executorService.shutdown();

ExecutorService executorService = Executors.newSingleThreadExecutor();
executorService.execute(new Runnable() {
public void run() {
System.out.println("Asynchronous task");
}
});
executorService.shutdown();

Future future = executorService.submit(new Runnable() {
public void run() {
System.out.println("Asynchronous task");
}
});
future.get();  //returns null if the task has finished correctly.

Future future = executorService.submit(new Callable(){
public Object call() throws Exception {
System.out.println("Asynchronous Callable");
return "Callable Result";
}
});
System.out.println("future.get() = " + future.get());

ExecutorService executorService = Executors.newSingleThreadExecutor();
Set<Callable<String>> callables = new HashSet<Callable<String>>();
callables.add(new Callable<String>() {
public String call() throws Exception {
return "Task 1";
}
});
callables.add(new Callable<String>() {
public String call() throws Exception {
return "Task 2";
}
});
callables.add(new Callable<String>() {
public String call() throws Exception {
return "Task 3";
}
});
String result = executorService.invokeAny(callables);
System.out.println("result = " + result);
executorService.shutdown();

ExecutorService executorService = Executors.newSingleThreadExecutor();
Set<Callable<String>> callables = new HashSet<Callable<String>>();
callables.add(new Callable<String>() {
public String call() throws Exception {
return "Task 1";
}
});
callables.add(new Callable<String>() {
public String call() throws Exception {
return "Task 2";
}
});
callables.add(new Callable<String>() {
public String call() throws Exception {
return "Task 3";
}
});
List<Future<String>> futures = executorService.invokeAll(callables);
for(Future<String> future : futures){
System.out.println("future.get = " + future.get());
}
executorService.shutdown();

ExecutorService 介绍

1. ThreadPoolExecutor
2. ScheduledThreadPoolExecutor

ExecutorService的创建

• newCachedThreadPool 创建一个可缓存的线程池,如果线程池长度超过处理需要,可灵活回收空闲线程,如果没有可以回收的,则新建线程。
• newFixedThreadPool 创建一个定长的线程池,可控制线程最大并发数,超出的线程会在队列中等待。
• newScheduledThreadPool 创建一个定长线程池,可以定时周期性执行任务。
• newSingleThreadPool 创建一个单线程线程池,它只会用唯一的线程来执行任务,保证所有任务按照指定顺序来执行(FIFO,LIFO)

ExecutorService的使用

ExecutorService executorService = Executors.newFixedThreadPool(10);
executorService.execute(new Runnable() {
public void run() {
System.out.println("入门小站");
}
});
executorService.shutdown();

ExecutorService的执行方法

• execute(Runnable)
• submit(Runnable)
• submit(Callable)
• invokeAny(...)
• invokeAll(...)

execute(Runnable) 无法获取执行结果

ExecutorService executorService = Executors.newSingleThreadExecutor();
executorService.execute(new Runnable() {
public void run() {
System.out.println("Asynchronous task");
}
});
executorService.shutdown();

submit(Runnable) 可以判断任务是否完成

Future future = executorService.submit(new Runnable() {
public void run() {
System.out.println("Asynchronous task");
}
});
future.get();  //returns null if the task has finished correctly.

submit(Callable)可以获取返回结果

Future future = executorService.submit(new Callable(){
public Object call() throws Exception {
System.out.println("Asynchronous Callable");
return "Callable Result";
}
});
System.out.println("future.get() = " + future.get());

invokeAny(...)

ExecutorService executorService = Executors.newSingleThreadExecutor();
Set<Callable<String>> callables = new HashSet<Callable<String>>();
callables.add(new Callable<String>() {
public String call() throws Exception {
return "Task 1";
}
});
callables.add(new Callable<String>() {
public String call() throws Exception {
return "Task 2";
}
});
callables.add(new Callable<String>() {
public String call() throws Exception {
return "Task 3";
}
});
String result = executorService.invokeAny(callables);
System.out.println("result = " + result);
executorService.shutdown();

invokeAll(...)

ExecutorService executorService = Executors.newSingleThreadExecutor();
Set<Callable<String>> callables = new HashSet<Callable<String>>();
callables.add(new Callable<String>() {
public String call() throws Exception {
return "Task 1";
}
});
callables.add(new Callable<String>() {
public String call() throws Exception {
return "Task 2";
}
});
callables.add(new Callable<String>() {
public String call() throws Exception {
return "Task 3";
}
});
List<Future<String>> futures = executorService.invokeAll(callables);
for(Future<String> future : futures){
System.out.println("future.get = " + future.get());
}
executorService.shutdown();

线程池ExecutorService的关闭

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