本節(jié)摘要：介紹線程優(yōu)先級(jí)，代碼示例
一、線程優(yōu)先級(jí)
線程優(yōu)先級(jí)的范圍是1~10桅咆，默認(rèn)優(yōu)先級(jí)是5，線程優(yōu)先級(jí)的主要作用是讓調(diào)度器優(yōu)先調(diào)度高優(yōu)先級(jí)線程坞笙，但這不意味著低優(yōu)先級(jí)線程得不到執(zhí)行岩饼，通常情況不需要修改線程優(yōu)先級(jí)，Thread類中有3個(gè)優(yōu)先級(jí)的常量：
二薛夜、源碼分析
public final void setPriority(int newPriority) {
ThreadGroup g;//線程所屬的線程組
checkAccess();
//設(shè)置的級(jí)別不能大于10且不能小于1
if (newPriority > MAX_PRIORITY || newPriority < MIN_PRIORITY) {
throw new IllegalArgumentException();
}
if((g = getThreadGroup()) != null) {
//設(shè)置的級(jí)別不能大于所屬線程組的最大級(jí)別
if (newPriority > g.getMaxPriority()) {
newPriority = g.getMaxPriority();
}
setPriority0(priority = newPriority);//本地方法
}
}
三籍茧、線程優(yōu)先級(jí)示例
public class ThreadPrioritiesDemo extends Thread {
private int priority;
public ThreadPrioritiesDemo(String name, int priority) {
super(name);
this.priority = priority;
}
public static void main(String[] args) {
Thread t1 = new ThreadPrioritiesDemo("thread1", 1);
Thread t2 = new ThreadPrioritiesDemo("thread2", 10);
t1.start();
t2.start();
}
@Override
public void run() {
Thread.currentThread().setPriority(priority);
for (int i = 0; i < 1000; i++) {
System.out.println(this + ":" + i);
if (i % 2 == 0)
Thread.yield();
}
}
}
輸出結(jié)果（截取部分）：
Thread[thread1,1,main]:670
Thread[thread2,10,main]:293
Thread[thread2,10,main]:294
Thread[thread1,1,main]:671
Thread[thread1,1,main]:672
Thread[thread2,10,main]:295
Thread[thread2,10,main]:296
Thread[thread1,1,main]:673
Thread[thread1,1,main]:674
Thread[thread2,10,main]:297
Thread[thread2,10,main]:298
Thread[thread1,1,main]:675
Thread[thread1,1,main]:676
Thread[thread2,10,main]:299
3.1、結(jié)果說(shuō)明
新開啟2個(gè)線程梯澜，線程1優(yōu)先級(jí)為1寞冯，線程2優(yōu)先級(jí)為10，兩個(gè)線程交替執(zhí)行，高優(yōu)先級(jí)線程（t2）并不是一直優(yōu)先于t1執(zhí)行
四吮龄、總結(jié)
高優(yōu)先級(jí)線程并不是一直優(yōu)于低優(yōu)先級(jí)線程執(zhí)行
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