Java多线程03_线程状态、优先级、用户线程和守护线程

刺骨的言语ヽ痛彻心扉 2022-12-01 14:05 294阅读 0赞

**Java多线程03\_线程状态、优先级、用户线程和守护线程**

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**线程方法：**

setPriority()				更改线程优先级
    static void sleep()			线程休眠
    void join()					插队
    static void yield()			礼让
    void interrupt()			中断线程
    boolean isAlive()			是否存活

**停止线程：**

**不推荐JDK提供的stop()、destory()方法 【已废弃】**

推荐让线程正常停止，不要死循环！

建议使用一个标志位进行终止，当flag=false，则终止线程运行

public class TestStop implements Runnable{ 
    
    	private boolean flag = true;
    	
    	@Override
    	public void run() { 
    		int i = 0;
    		while(flag) { 
    			System.out.println("run...Thread"+i++);
    		}
    	}
    	
    	//设置公开方法利用标志位停止线程
    	public void stopThread() { 
    		this.flag = false;
    		System.out.println("线程停止了");
    	}
    	
    	public static void main(String[] args) { 
    		TestStop testStop = new TestStop();
    		new Thread(testStop).start();
    		
    		for(int i=0;i<1000;i++) { 
    			System.out.println("main...,"+i);
    			if(i==900) { 
    				testStop.stopThread();
    			}
    		}
    		
    	}
    	
    }

**线程休眠：**

**sleep方法存在异常：InterruptedException**

**sleep时间结束，线程进入就绪状态**

**每个对象都有一个锁，sleep不会释放锁**

Thread.sleep(1000);

**线程礼让：**

**让当前执行的线程暂停，但不阻塞**

**将线程从运行状态转为就绪状态**

**礼让不一定成功，看cpu心情**

Thread.yield();

**Join合并线程，待此线程执行完成后，再执行其他线程，其他线程阻塞（插队）**

main线程和Thread线程交替执行，当main线程执行到200时，Thread线程插队，一直到执行结束，main线程才能重新执行

package com.blu.demo1;
    
    public class TestJoin implements Runnable{ 
    
    	@Override
    	public void run() { 
    		for(int i = 0;i < 1000;i++) { 
    			System.out.println("vip线程正在执行....."+i);
    		}
    	}
    	
    	public static void main(String[] args) throws InterruptedException { 
    		TestJoin testJoin = new TestJoin();
    		Thread thread = new Thread(testJoin);
    		thread.start();
    		
    		for(int i = 0;i < 1000;i++) { 
    			if(i==200) { 
    				thread.join();
    			}
    			System.out.println("main线程正在执行....."+i);
    		}
    	}
    
    }

**getState()监测线程状态：**

**返回枚举类型：**

NEW	
    RUNNABLE
    BLOCKED
    WAITING
    TIMED_WAITING
    TERMINATED

**线程优先级：**

**线程优先级用1-10之间的整数表示，1为最低优先级，10为最高优先级**

**主线程优先级默认为5，且不可修改**

**枚举**  
**Thread.MAX\_PRIORITY = 10**  
**Thread.NORM\_PRIORITY = 5**  
**Thread.MIN\_PRIORITY = 1**

**优先级高不一定先执行，由CPU调度决定**

public class TestPriority { 
    	
    	public static void main(String[] args) { 
    		//主线程优先级
    		System.out.println(Thread.currentThread().getName()+"-->"+Thread.currentThread().getPriority());
    		MyPriority myPriority = new MyPriority();
    		Thread t1 = new Thread(myPriority);
    		Thread t2 = new Thread(myPriority);
    		Thread t3 = new Thread(myPriority);
    		Thread t4 = new Thread(myPriority);
    		Thread t5 = new Thread(myPriority);
    		Thread t6 = new Thread(myPriority);
    		//设置优先级
    		t1.start();
    		t2.setPriority(1);
    		t3.setPriority(4);
    		t4.setPriority(Thread.MAX_PRIORITY);
    		t5.setPriority(5);
    		t6.setPriority(7);
    		t2.start();
    		t3.start();
    		t4.start();
    		t5.start();
    		t6.start();
    	}
    	
    }
    
    class MyPriority implements Runnable{ 
    
    	@Override
    	public void run() { 
    		System.out.println(Thread.currentThread().getName()+"-->"+Thread.currentThread().getPriority());
    	}
    	
    }

**守护线程**

**线程分为用户线程（比如main） 和 守护线程（比如gc）**

**虚拟机必须确保用户线程执行完毕，不用等待守护线程执行完毕**

当只剩下守护线程时，JVM就会退出，只要存在一个用户线程，JVM就不会退出

public class TestDaemon { 
    	
    	public static void main(String[] args) { 
    		God god = new God();
    		You you = new You();
    		Thread thread = new Thread(god);
    		thread.setDaemon(true);
    		thread.start();
    		new Thread(you).start();
    	}
    }
    
    class God implements Runnable{ 
    	
    	@Override
    	public void run() { 
    		while(true) { 
    			System.out.println("上帝保佑着你");
    		}
    	}
    }
    
    class You implements Runnable{ 
    
    	@Override
    	public void run() { 
    		for(int i = 0;i<=100;i++) { 
    			System.out.println("你开心地活了"+i+"年");
    		}
    		System.out.println("GoodBye,World!");
    	}
    	
    }

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