Thread类的setPriority()方法用于设置更改线程的优先级。每个线程都有一个优先级，由1到10之间的整数表示。
Thread类提供3个常量属性:
public static int MIN_PRIORITY:它是线程的最大优先级，它的值是1。public static int NORM_PRIORITY:这是线程的普通优先级，它的值是5。public static int MAX_PRIORITY:它是线程的最小优先级，它的值是10。
还可以将线程的优先级设置在1到10之间。此优先级称为自定义优先级或用户定义的优先级。
语法
a:将此线程设置为优先级。
异常
IllegalArgumentException:如果优先级不在MIN_PRIORITY到MAX_PRIORITY的范围内，则抛出此异常。SecurityException:如果当前线程无法修改此线程，则抛出此异常。
示例一 :最大优先级线程
public class JavaSetPriorityExp1 extends Thread
{
public void run()
{
System.out.println("Priority of thread is: "+Thread.currentThread().getPriority());
}
public static void main(String args[])
{
// creating one thread
JavaSetPriorityExp1 t1=new JavaSetPriorityExp1();
// print the maximum priority of this thread
t1.setPriority(Thread.MAX_PRIORITY);
// call the run() method
t1.start();
}
}
执行上面示例代码，得到以下结果:
Priority of thread is: 10
示例二 :最小优先级线程
public class JavaSetPriorityExp2 extends Thread
{
public void run()
{
System.out.println("Priority of thread is: "+Thread.currentThread().getPriority());
}
public static void main(String args[])
{
// creating one thread
JavaSetPriorityExp2 t1=new JavaSetPriorityExp2();
// print the minimum priority of this thread
t1.setPriority(Thread.MIN_PRIORITY);
// This will call the run() method
t1.start();
}
}
执行上面示例代码，得到以下结果:
Priority of thread is: 1
示例三 ：正常优先级线程
public class JavaSetPriorityExp3 extends Thread
{
public void run()
{
System.out.println("Priority of thread is: "+Thread.currentThread().getPriority());
}
public static void main(String args[])
{
// creating one thread
JavaSetPriorityExp3 t1=new JavaSetPriorityExp3();
// print the normal priority of this thread
t1.setPriority(Thread.NORM_PRIORITY);
// starting the thread
t1.start();
}
}
执行上面示例代码，得到以下结果:
Priority of thread is: 5
示例四 ：用户定义优先级线程
public class JavaSetPriorityExp4 extends Thread
{
public void run()
{
System.out.println("running...");
}
public static void main(String args[])
{
// creating one thread
JavaSetPriorityExp4 t1=new JavaSetPriorityExp4();
JavaSetPriorityExp4 t2=new JavaSetPriorityExp4();
// set the priority
t1.setPriority(4);
t2.setPriority(7);
// print the user defined priority
System.out.println("Priority of thread t1 is: " + t1.getPriority()); //4
System.out.println("Priority of thread t2 is: " + t2.getPriority()); //7
// this will call the run() method
t1.start();
}
}
执行上面示例代码，得到以下结果:
Priority of thread t1 is: 4
Priority of thread t2 is: 7
running...
示例五 ：当优先级大于10时
public class JavaSetPriorityExp5 extends Thread
{
public void run()
{
System.out.println("running...");
}
public static void main(String args[])
{
// creating one thread
JavaSetPriorityExp5 t1=new JavaSetPriorityExp5();
JavaSetPriorityExp5 t2=new JavaSetPriorityExp5();
// set the priority
t1.setPriority(12);
t2.setPriority(7);
// print exception because priority of t1 is greater than 10
System.out.println("Priority of thread t1 is: " + t1.getPriority());
System.out.println("Priority of thread t2 is: " + t2.getPriority());
// call the run() method
t1.start();
}
}
执行上面示例代码，得到以下结果:
Exception in thread "main" java.lang.IllegalArgumentException
at java.lang.Thread.setPriority(Thread.java:1089)
at JavaSetPriorityExp5.main(JavaSetPriorityExp5.java:13)
