并发
并发编程∶并发、并行
并发（多线程操作同一个资源)
CPU一核，模拟出来多条线程，天下武功，唯快不破，快速交替并行(多个人一起行走)
CPU 多核，多个线程可以同时执行;
public class QuickSort {public static void main(String[] args) {//获取cpu核数System.out.println(Runtime.getRuntime().availableProcessors());}
线程有六种状态
线程wait 和 sleep的区别
- wait：会释放锁 sleep会抱着锁睡不释放
- wait： sleep：在任何地方睡
- wait：不会捕获异常 sleep：必须要捕获异常
代码来展示并发（传统Synchronized）
public class QuickSort {public static void main(String[] args) {//并发，多个线程操作一个资源类 把资源丢入线程Ticket tic=new Ticket();//Lambda表达式（参数)->{代码}
/* new Thread(new Runnable() {@Overridepublic void run() {}}).start();*/new Thread(()->{for (int i = 0; i < 60; i++) {tic.sale();}},"A").start();new Thread(()->{for (int i = 0; i < 60; i++) {tic.sale();}},"B").start();new Thread(()->{for (int i = 0; i < 60; i++) {tic.sale();}},"C").start();}
}
class Ticket{private int number =50;public synchronized void sale(){if(number>0){System.out.println(Thread.currentThread().getName()+"卖出了"+number--+"剩下"+number);}}
}
Lock
公平锁：十分公平 可以分先来后到
非公平锁： 十分不公平 可以插队
public class QuickSort {public static void main(String[] args) {//并发，多个线程操作一个资源类 把资源丢入线程Ticket tic=new Ticket();new Thread(new Runnable() {@Overridepublic void run() {}}).start();new Thread(()->{for (int i = 0; i < 60; i++) {tic.sale();}},"A").start();new Thread(()->{for (int i = 0; i < 60; i++) {tic.sale();}},"B").start();new Thread(()->{for (int i = 0; i < 60; i++) {tic.sale();}},"C").start();}
}
/*Lock三部曲1 new ReentrantLock();2 新ReentrantLock()3 finaLly=> lock. unLock(); (/解锁*/
class Ticket{private int number=50;Lock lock=new ReentrantLock();public void sale(){lock.lock();if(number>0){System.out.println(Thread.currentThread().getName()+"卖出了"+number--+"剩下"+number);}lock.unlock();}
}
结果
Synchronized和Lock区别
- Synchronized内置的Java关键字，Lock是一个Java类
- Synchronized 无法判断获取锁的状态，Lock 可以判断是否获取到了锁
- Synchronized 会自动释放锁，lock必须要手动释放锁!如果不释放锁，死锁
- Synchronized线程1（获得锁，阻塞)、线程2(等待，傻傻的等）
- Synchronized可重入锁，不可以中断的，非公平;Lock，可重入锁，可以判断锁，非公平(可以自己设置); 同步可重入锁，不可以中断的，非公平；锁，可重入锁，可以判断锁，非公平(可以自己设置)；
什么是锁
生产者和消费者问题
代码
public class QuickSort {public static void main(String[] args) {Data data=new Data();new Thread(()->{try {data.printA();} catch (InterruptedException e) {throw new RuntimeException(e);}},"A").start();new Thread(()->{try {data.printB();} catch (InterruptedException e) {throw new RuntimeException(e);}},"B").start();new Thread(()->{try {data.printC();} catch (InterruptedException e) {throw new RuntimeException(e);}},"C").start();}
}
class Data{private Lock lock=new ReentrantLock();//监视器conditionprivate Condition condition =lock.newCondition();private Condition condition1 =lock.newCondition();private Condition condition2 =lock.newCondition();private int number=1;public void printA() throws InterruptedException {lock.lock();//业务 判断-》执行-》通知while (number!=1){//等待condition.await();}System.out.println(Thread.currentThread().getName()+"A");number=2;condition.signal();lock.unlock();}public void printB() throws InterruptedException {lock.lock();//业务 判断-》执行-》通知while (number!=2){//等待condition1.await();}System.out.println(Thread.currentThread().getName()+"B");number=3;condition.signal();lock.unlock();}public void printC() throws InterruptedException {lock.lock();//业务 判断-》执行-》通知while (number!=3){//等待condition2.await();}System.out.println(Thread.currentThread().getName()+"C");number=1;condition.signal();lock.unlock();}
}
