Java多线程相关的两个类:
- Thread,需要继承
- Runnable，需要实现这个接口
相同点： 1.都要实现run方法，调用时使用start方法。 2.Thread也是实现Runnable
不同点： 1.Thread不适合资源共享 class hello extends Thread { public void run() { for (int i = 0; i < 7; i++) { if (count > 0) { System.out.println("count= " + count--); } } }
public static void main(String[] args) { hello h1 = new hello(); hello h2 = new hello(); hello h3 = new hello(); h1.start(); h2.start(); h3.start(); } private int count = 5;} 输出时,count不能够共享 2. Runnable可以实现共享
class MyThread implements Runnable{ private int ticket = 5; //5张票 public void run() { for (int i=0; i<=20; i++) { if (this.ticket > 0) { System.out.println(Thread.currentThread().getName()+ "正在卖票"+this.ticket--); } } } }public class lzwCode { public static void main(String [] args) { MyThread my = new MyThread(); new Thread(my, "1号窗口").start(); new Thread(my, "2号窗口").start(); new Thread(my, "3号窗口").start(); } } 此时，输出结果为： ![在此输入图片描述][1] [1]: 3. 线程同步 共享资源变量时，需要资源同步 同步时，分为同步对象与同步方法两种情形： 3.1 同步对象 synchronized（同步对象）{ //需要同步的代码 } 如买票问题： class hello implements Runnable { public void run() { for(int i=0;i<10;++i){ synchronized (this) { if(count>0){ try{ Thread.sleep(1000); }catch(InterruptedException e){ e.printStackTrace(); } System.out.println(count--); } } } }
public static void main(String[] args) { hello he=new hello(); Thread h1=new Thread(he); Thread h2=new Thread(he); Thread h3=new Thread(he); h1.start(); h2.start(); h3.start(); } private int count=5;} 3.2 方法同步： 同如买票问题： class hello implements Runnable { public void run() { for (int i = 0; i < 10; ++i) { sale(); } }
public synchronized void sale() { if (count > 0) { try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println(count--); } } public static void main(String[] args) { hello he = new hello(); Thread h1 = new Thread(he); Thread h2 = new Thread(he); Thread h3 = new Thread(he); h1.start(); h2.start(); h3.start(); } private int count = 5;} 3.3生产者和消费者问题 示例代码： class Info {
public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } private String name = "Rollen"; private int age = 20;} class Producer implements Runnable{ private Info info=null; Producer(Info info){ this.info=info; } public void run(){ boolean flag=false; for(int i=0;i<25;++i){ if(flag){ this.info.setName("Rollen"); try{ Thread.sleep(100); }catch (Exception e) { e.printStackTrace(); } this.info.setAge(20); flag=false; }else{ this.info.setName("chunGe"); try{ Thread.sleep(100); }catch (Exception e) { e.printStackTrace(); } this.info.setAge(100); flag=true; } } }}class Consumer implements Runnable{ private Info info=null; public Consumer(Info info){ this.info=info; } public void run(){ for(int i=0;i<25;++i){ try{ Thread.sleep(100); }catch (Exception e) { e.printStackTrace(); } System.out.println(this.info.getName()+"<---->"+this.info.getAge()); } }} class hello{ public static void main(String[] args) { Info info=new Info(); Producer pro=new Producer(info); Consumer con=new Consumer(info); new Thread(pro).start(); new Thread(con).start(); }} 问题：错位； 解决办法：添加同步； class Info {
public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public synchronized void set(String name, int age){ this.name=name; try{ Thread.sleep(100); }catch (Exception e) { e.printStackTrace(); } this.age=age; } public synchronized void get(){ try{ Thread.sleep(100); }catch (Exception e) { e.printStackTrace(); } System.out.println(this.getName()+"<===>"+this.getAge()); } private String name = "Rollen"; private int age = 20;} class Producer implements Runnable { private Info info = null; Producer(Info info) { this.info = info; } public void run() { boolean flag = false; for (int i = 0; i < 25; ++i) { if (flag) { this.info.set("Rollen", 20); flag = false; } else { this.info.set("ChunGe", 100); flag = true; } } }} class Consumer implements Runnable { private Info info = null; public Consumer(Info info) { this.info = info; } public void run() { for (int i = 0; i < 25; ++i) { try { Thread.sleep(100); } catch (Exception e) { e.printStackTrace(); } this.info.get(); } }}class hello { public static void main(String[] args) { Info info = new Info(); Producer pro = new Producer(info); Consumer con = new Consumer(info); new Thread(pro).start(); new Thread(con).start(); }} 问题：出现重复读，重复写； 解决办法：加入等待和通知； class Info {
public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public synchronized void set(String name, int age){ if(!flag){ try{ super.wait(); }catch (Exception e) { e.printStackTrace(); } } this.name=name; try{ Thread.sleep(100); }catch (Exception e) { e.printStackTrace(); } this.age=age; flag=false; super.notify(); } public synchronized void get(){ if(flag){ try{ super.wait(); }catch (Exception e) { e.printStackTrace(); } } try{ Thread.sleep(100); }catch (Exception e) { e.printStackTrace(); } System.out.println(this.getName()+"<===>"+this.getAge()); flag=true; super.notify(); } private String name = "Rollen"; private int age = 20; private boolean flag=false;}class Producer implements Runnable { private Info info = null; Producer(Info info) { this.info = info; } public void run() { boolean flag = false; for (int i = 0; i < 25; ++i) { if (flag) { this.info.set("Rollen", 20); flag = false; } else { this.info.set("ChunGe", 100); flag = true; } } }} class Consumer implements Runnable { private Info info = null; public Consumer(Info info) { this.info = info; } public void run() { for (int i = 0; i < 25; ++i) { try { Thread.sleep(100); } catch (Exception e) { e.printStackTrace(); } this.info.get(); } }} class hello { public static void main(String[] args) { Info info = new Info(); Producer pro = new Producer(info); Consumer con = new Consumer(info); new Thread(pro).start(); new Thread(con).start(); }}