Java Thread | 线程

Why Thread

• Single-threaded application:
  1. leads to poor response
  2. has poor prefomance
  3. has poor utilization of CPU resources
     
     

Thread in Java

• A/multiple thread is one/multiple task of an/- execution flow, flowing from beginning to end
• Organzied programs into logically seperate paths
• Can preform independent
• Share access to common resources.
  
  
  
  
• Language and api provide concurrency in JAVA
• Multiple thread if execution
• Each thread has its own method-call stack
• 程序计数器

---

Life cycle of a thread

• Controlled by JVM

1. New
   在调取start（）之前， 创建 thread class 的实例
2. Runnable
   调取start（）之后
3. Running
   scheduler被选中
4. Non-Runnable(Blocked)
   thread alive，but currently not eligible to run
5. Terminated
   run()还在的时候死掉了

---

Syntax：

1. extend Thread Class

public class ClassName extends Thread{
	public void run(){
	//run 必须override
	}
}

2. runnable obj

public class ClassName implements Runnable{
	public void run(){
	//run 必须实现 和 override
	//只有一个run（）方法
	}
}

---

Thread Schedular

• JVM
• Decides which thread should run
• Random select
• Preemptive: priority
• Time slicing scheduling:predifine->reenter

---

Intrinsic lock

• Protect multi-thread task
• Fac to every obj
• Dadada

---

好处

• prevent thread interference
• Prevent consistency problem

---

同步种类

• By process
• By Thread
• (inter-thread communication)
• Mutual exclusive

Synchronized void method(…){
}

Synchronized(this){
}

---

Sleep()

• Purpose: use to sleep a thread for a setting time.
• Implimentation:

// runnable implements
// main()
@ Override
public void run(){
// some code here
	try{
		Thread.sleep(1000);//sleep for 1 second
		}catch(InterruptedException e{
			System.out.println(e);
		}
// some code here
}

---

join()

• Purpose: use to forced one thread to wait for antoher thread to finish.
• Implimentation:

 // main()
 // some code here
 thread1.start()
 try{
 	thread1.join();
 }catch(InterruptedException e{
			System.out.println(e);
}
thread2.start();
//some code here

---

interrupt()

• use to “terminated” the status of a task
• 常用表达 Thread.CurrentThread().isInterrupted()