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创立线程的办法
- 继承 Thread 类
- 继承 Thread 类，重写 run 办法，通过线程类实例.start()办法开启线程。
public class TestThread1 extends Thread{
@override
public void run(){System.out.println("线程 run 办法！");
}
public static void main(String){new TestThread1().start();}
}
-
实现 Runnable 接口
- 实现 Runnable 接口，重写 run 办法，通过 new Thread(线程类实例).start() 开启线程
- 举荐应用该形式，防止 java 的单继承局限性
public class TestThread2 implements Runnable{
@Override
public void run() {System.out.println("线程 run 办法！");
}
public static void main(String[] args) {new Thread(new TestThread2()).start();}
}
- 实现 Callable 接口
-
实现 Callable 接口，重写 call 办法，call 办法有返回值
-
启动形式：
- 创立执行服务
- 提交执行
- 获取后果
- 敞开服务
-
public class TestThread2 implements Callable{
@Override
public Boolean call() {System.out.println("线程 call 办法！");
return true;
}
public static void main(String[] args) throws InterruptedException, ExecutionException {TestThread2 t1 = new TestThread2();
TestThread2 t2 = new TestThread2();
TestThread2 t3 = new TestThread2();
// 创立执行服务
ExecutorService ser = Executors.newFixedThreadPool(3);
// 提交执行
Future<Boolean> r1 = ser.submit(t1);
Future<Boolean> r2 = ser.submit(t2);
Future<Boolean> r3 = ser.submit(t3);
// 获取后果
boolean rs1 = r1.get();
boolean rs2 = r2.get();
boolean rs3 = r3.get();
// 敞开服务
ser.shutdownNow();}
线程同步
- 多个线程同时操作同一资源，线程不平安，变量值错乱
- 加锁
- 队列 + 锁(synchronized)
- synchronized 默认锁 this，能够显示指定锁的对象来批改
1. synchronized 润饰办法，线程平安办法
public class TestThreadSafe {public static void main(String[] args) {BuyTicket bt1 = new BuyTicket();
Thread thread1 = new Thread(bt1,"张三");
Thread thread2 = new Thread(bt1,"李四");
Thread thread3 = new Thread(bt1,"黄牛");
thread1.start();
thread2.start();
thread3.start();}
}
class BuyTicket implements Runnable{
private int ticketNumber = 10;
private boolean flag = true;
@Override
public void run() {while(flag) {
try {buy();
} catch (InterruptedException e) {e.printStackTrace();
}
}
}
public synchronized void buy() throws InterruptedException {
// 买票
if(ticketNumber <= 0){System.out.println("票卖完了！");
flag = false;
return;
}
Thread.sleep(100);
//Thread.yield();
System.out.println(Thread.currentThread().getName() + "买到了一张票，还剩下"+(--ticketNumber) + "张票！");
}
}
2. synchronized 润饰代码块，线程平安代码块
public class TestThreadSafe {public static void main(String[] args) {BuyTicket bt1 = new BuyTicket();
Thread thread1 = new Thread(bt1,"张三");
Thread thread2 = new Thread(bt1,"李四");
Thread thread3 = new Thread(bt1,"黄牛");
thread1.start();
thread2.start();
thread3.start();}
}
class BuyTicket implements Runnable{
private int ticketNumber = 10;
private boolean flag = true;
@Override
public void run() {while(flag) {System.out.println(Thread.currentThread().getName() + "筹备买票" + flag);
try {buy();
} catch (InterruptedException e) {e.printStackTrace();
}
}
}
public void buy() throws InterruptedException {synchronized(this){
// 买票
if(ticketNumber <= 0){
flag = false;
System.out.println("票卖完了！");
return;
}
Thread.sleep(100);
//Thread.yield();
System.out.println(Thread.currentThread().getName() + "买到了一张票，还剩下"+(--ticketNumber) + "张票！");
}
}
}
3. 应用可反复锁 ReentrantLock
import java.util.concurrent.locks.ReentrantLock;
public class TestLock {public static void main(String[] args) {BuyTicket bt1 = new BuyTicket();
Thread thread1 = new Thread(bt1,"张三");
Thread thread2 = new Thread(bt1,"李四");
Thread thread3 = new Thread(bt1,"黄牛");
thread1.start();
thread2.start();
thread3.start();}
}
class BuyTicket implements Runnable{
private int ticketNumber = 1000;
private boolean flag = true;
// 定义可反复锁
private final ReentrantLock lock = new ReentrantLock();
@Override
public void run() {while(flag) {
try {buy();
} catch (InterruptedException e) {e.printStackTrace();
}
}
}
public void buy() throws InterruptedException {lock.lock();
// 买票
if(ticketNumber <= 0){System.out.println("票卖完了！");
flag = false;
}else {Thread.sleep(100);
//Thread.yield();
System.out.println(Thread.currentThread().getName() + "买到了一张票，还剩下"+(--ticketNumber) + "张票！");
}
lock.unlock();}
}
-
死锁
- 两个以上的对象锁，每个线程相互占有对方须要的资源。造成死锁。
线程状态
- 新生状态（new）
- 就绪状态（start）
- 阻塞状态（sleep、wait、同步锁定）
- 运行状态
- 死亡状态 线程对象进入死亡状态后，将不能再次调用 start()办法再次启动
线程（Thread 类）办法
- setPriority(int newPriority) 更改线程优先级 newPriority 从 1 到 10
- static void sleep(long millis) 使以后正在执行的线程休眠指定毫秒，不会开释线程锁对象
- void join() 线程合并，期待该线程终止
- static void yield() 暂停以后正在执行的线程，执行其它线程
- void interrupt() 中断线程
- boolean isAlive() 该线程是否沉闷
守护线程
- setDaemon(true) : 设置为守护线程
- 线程分为用户线程和守护线程
- JVM 虚拟机确保用户线程执行结束
- JVM 虚拟机不必期待守护线程执行结束
eg：后盾记录操作日志，监控内存，垃圾回收期待
最初
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