多线程

线程是操作系统能够进入运算调度的最小单位。它被包含在进程之中，是进程中的实际运作单位。

进程：是程序的基本执行实体。

并发：在同一个时刻，有多个指令在单个CPU上交替执行。

并行：在同一时刻，有多个指令在多个CPU上同时执行。

多线程的实现方式

1.继承Thread类的方式进行实现

package MyThread;public class MyThread extends Thread{@Overridepublic void run(){for (int i = 0; i < 100; i++) {System.out.println(getName()+"helloworld");}}
}
package MyThread;public class ThreadDemo {public static void main(String[] args) {
MyThread t1=new MyThread();MyThread t2=new MyThread();t1.setName("线程1");t2.setName("线程2");
t1.start();
t2.start();}
}

2.实现Runnable接口的方式进行实现

package MyThread.a02ThreadDemo02;public class MyRun implements Runnable{@Overridepublic void run() {Thread t = Thread.currentThread();for (int i = 0; i < 100; i++) {System.out.println(t.getName()+"Helloworld");}}
}
package MyThread.a02ThreadDemo02;public class ThreadDemo {public static void main(String[] args) {MyRun mr=new MyRun();Thread t1=new Thread(mr);Thread t2=new Thread(mr);t1.setName("线程1");t2.setName("线程2");t1.start();t2.start();}
}

3.利用Callable接口和Future接口方式实现

package MyThread.a03ThreadDemo03;import java.util.concurrent.Callable;public class MyCallable implements Callable<Integer> {@Overridepublic Integer call() throws Exception {int sum=0;for (int i = 0; i < 100; i++) {sum=sum+i;}return sum;}
}
package MyThread.a03ThreadDemo03;import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;public class ThreadDemo {public static void main(String[] args) throws ExecutionException, InterruptedException {MyCallable mc=new MyCallable();FutureTask<Integer> ft=new FutureTask<>(mc);Thread t1=new Thread();t1.start();Integer result = ft.get();System.out.println(result);}
}

常见的成员方法

package MyThread.a04ThreadDemo;public class MyThread extends Thread{public MyThread() {}
public MyThread(String name){super(name);
}@Overridepublic void run(){for (int i = 0; i < 100; i++) {System.out.println(getName()+"@"+i);}}
}
package MyThread.a04ThreadDemo;public class ThreadDemo {public static void main(String[] args) {//getName//1.如果我们没有给线程设置名字，线程也是有默认的名字的//格式：Thread-x(x序号，从0开始的)//2.如果我们要给线程设置名字，可以用set方法进行设置，也可以用构造方法//当jvm虚拟机启动之后，会自动的启动多条线程，其中有一条线程就叫main线程//它的作用就是调用main方法，并执行里面的代码/* MyThread t1=new MyThread();MyThread t2=new MyThread();MyThread t3=new MyThread("karry");MyThread t4=new MyThread("roy");t1.start();t2.start();*///哪条线程执行到这个方法，此时获取的就是哪条线程的对象
Thread t=new Thread();String name = t.getName();System.out.println(name);}
}

线程的优先级

package MyThread.a05threadDEMO;public class MyRun implements Runnable{@Overridepublic void run() {for (int i = 0; i < 100; i++) {System.out.println(Thread.currentThread().getName()+i);}}
}
package MyThread.a05threadDEMO;public class ThreadDemo {public static void main(String[] args) {MyRun mr=new MyRun();Thread t1=new Thread(mr,"karry");Thread t2=new Thread(mr,"roy");System.out.println(t1.getPriority());System.out.println(t2.getPriority());t1.setPriority(1);t2.setPriority(10);t1.start();t2.start();}
}

守护线程

package MyThread.a06threaddemo;public class MyThread1 extends  Thread{@Overridepublic void run() {for (int i = 0; i < 100; i++) {System.out.println(getName()+"@"+i);}}
}
package MyThread.a06threaddemo;public class MyThread2 extends Thread{@Overridepublic void run() {for (int i = 0; i < 100; i++) {System.out.println(getName()+"@"+i);}}
}package MyThread.a06threaddemo;import MyThread.a04ThreadDemo.MyThread;public class ThreadDemo {public static void main(String[] args) {MyThread1 t1=new MyThread1();MyThread2 t2=new MyThread2();t1.setName("karry");t2.setName("roy");t2.setDaemon(true);t1.start();t2.start();}
}