java并发：初探用户线程和守护线程
2024-09-07 00:03:33
用户线程和守护线程
用户线程
用户线程执行完，jvm退出。守护线程还是可以跑的
/**
* A <i>thread</i> is a thread of execution in a program. The Java
* Virtual Machine allows an application to have multiple threads of
* execution running concurrently.
* <p>
* Every thread has a priority. Threads with higher priority are
* executed in preference to threads with lower priority. Each thread
* may or may not also be marked as a daemon. When code running in
* some thread creates a new <code>Thread</code> object, the new
* thread has its priority initially set equal to the priority of the
* creating thread, and is a daemon thread if and only if the
* creating thread is a daemon.
* <p>
* When a Java Virtual Machine starts up, there is usually a single
* non-daemon thread (which typically calls the method named
* <code>main</code> of some designated class). The Java Virtual
* Machine continues to execute threads until either of the following
* occurs:
* <ul>
* <li>The <code>exit</code> method of class <code>Runtime</code> has been
* called and the security manager has permitted the exit operation
* to take place.
* <li>All threads that are not daemon threads have died, either by
* returning from the call to the <code>run</code> method or by
* throwing an exception that propagates beyond the <code>run</code>
* method.
* </ul>
* /
用户线程优先权
例子
package com.java.javabase.thread.base;
import lombok.extern.slf4j.Slf4j;
@Slf4j
public class PriorityTest {
private static int size =10;
public static void main(String[] args) {
Thread t1 =new ThreadOne("t1");
Thread t2 =new ThreadOne("t2");
t2.setPriority(1);
t1.start();
t2.start();
log.info("Thread {} prority is {}",Thread.currentThread().getName(),Thread.currentThread().getPriority());
}
static class ThreadOne extends Thread{
public ThreadOne(String name){
super(name);
}
@Override
public void run(){
int i =0;
while(i<size){
log.info("Thread : {} priority is {} ,run {} times",Thread.currentThread().getName(),
Thread.currentThread().getPriority(),i++);
}
}
}
}
说明
setPriority是Thread方法，用户线程的优先级是1到10，默认是5。虽然设置了优先级，但线程的执行还是在于获取cpu的执行，看操作系统的支持，
不是你级别高，cpu就给你用的。
守护线程
package com.java.javabase.thread.base;
import lombok.extern.slf4j.Slf4j;
@Slf4j
public class DaemonTest {
private static int size =10;
public static void main(String[] args) {
Thread t1 =new ThreadOne("t1");
Thread t2 =new ThreadTwo("t2");
t2.setDaemon(true);
t1.start();
t2.start();
log.info("Thread {} prority is {}",Thread.currentThread().getName(),Thread.currentThread().getPriority());
}
static class ThreadOne extends Thread{
public ThreadOne(String name){
super(name);
}
@Override
public void run(){
int i =0;
while(i<size){
try {
Thread.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
log.info("Thread : {} priority is {} ,run {} times",Thread.currentThread().getName(),
Thread.currentThread().getPriority(),i++);
}
}
}
static class ThreadTwo extends Thread{
public ThreadTwo(String name){
super(name);
}
@Override
public void run(){
int i =0;
while(true&& i<(size*10000)){
try {
Thread.sleep(20);
} catch (InterruptedException e) {
e.printStackTrace();
}
log.info("Thread : {} priority is {} ,run {} times",Thread.currentThread().getName(),
Thread.currentThread().getPriority(),i++);
}
}
}
}
测试结果
2019-07-30 20:49:51,963 [main] INFO DaemonTest - Thread main prority is 5
2019-07-30 20:49:51,970 [t1] INFO DaemonTest - Thread : t1 priority is 5 ,run 0 times
2019-07-30 20:49:51,980 [t1] INFO DaemonTest - Thread : t1 priority is 5 ,run 1 times
2019-07-30 20:49:51,980 [t2] INFO DaemonTest - Thread : t2 priority is 5 ,run 0 times
2019-07-30 20:49:51,991 [t1] INFO DaemonTest - Thread : t1 priority is 5 ,run 2 times
2019-07-30 20:49:52,001 [t2] INFO DaemonTest - Thread : t2 priority is 5 ,run 1 times
2019-07-30 20:49:52,002 [t1] INFO DaemonTest - Thread : t1 priority is 5 ,run 3 times
2019-07-30 20:49:52,013 [t1] INFO DaemonTest - Thread : t1 priority is 5 ,run 4 times
2019-07-30 20:49:52,021 [t2] INFO DaemonTest - Thread : t2 priority is 5 ,run 2 times
2019-07-30 20:49:52,023 [t1] INFO DaemonTest - Thread : t1 priority is 5 ,run 5 times
2019-07-30 20:49:52,034 [t1] INFO DaemonTest - Thread : t1 priority is 5 ,run 6 times
2019-07-30 20:49:52,042 [t2] INFO DaemonTest - Thread : t2 priority is 5 ,run 3 times
2019-07-30 20:49:52,045 [t1] INFO DaemonTest - Thread : t1 priority is 5 ,run 7 times
2019-07-30 20:49:52,056 [t1] INFO DaemonTest - Thread : t1 priority is 5 ,run 8 times
2019-07-30 20:49:52,062 [t2] INFO DaemonTest - Thread : t2 priority is 5 ,run 4 times
2019-07-30 20:49:52,066 [t1] INFO DaemonTest - Thread : t1 priority is 5 ,run 9 times
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