1.概念理解
进程：是操作系统结构的基础；是一次程序的执行；是一个程序及其数据在处理机上顺序执行时所发生的活动；是程序在一个数据
集合上运行的过程，它是系统进行资源分配和调度的一个独立单位。
线程：是在进程中独立运行的子任务。
多线程的优点：可以最大限度的利用cpu的空闲时间来处理其他任务。
线程实现：
线程可以通过集成Thread ：但是java不支持多继承。
实现Runable接口
注意点：执行start（）方法的顺序不代表线程启动的顺序。
2：对比数据的共享
public class ConThread extends Thread{
public int count=5;
public String name;
public ConThread(String name){
this.name=name;
this.setName(name);
}
@Override
public void run() {
// TODO Auto-generated method stub
super.run();
if(count>0){
count--;
System.out.println("this Thread name is :"+this.currentThread().getName()+"--"+count);
}
}
}
ConThread th1=new ConThread("A");
ConThread th2=new ConThread("B");}}
ConThread th3=new ConThread("C");
ConThread th4=new ConThread("D");
th1.start();
th2.start();
th3.start();
th4.start()
以上的线程通过newThread之间创建start，数据count并不会共享，每个线程都会输出4,3,2,1,
public class ConThread extends Thread{
public int count=5;
public String name;
public ConThread(){
}
@Override
public void run() {
// TODO Auto-generated method stub
super.run();
// while(count>0){
count--;
System.out.println("this Thread name is :"+this.currentThread().getName()+"--"+count);
//}
}
}
ConThread th=new ConThread();
Thread th0=new Thread(th,"A");
Thread th1=new Thread(th,"B");
Thread th2=new Thread(th,"C");
th0.start();
th1.start();
th2.start();
以上线程则是传入构造方法，创建Thread，则会共享数据count，但是线程非安全。
3: synchronized 关键字
public class ConThread extends Thread{
public int count=5;
public String name;
public ConThread(){
}
@Override
synchronized public void run() {
// TODO Auto-generated method stub
super.run();
// while(count>0){
count--;
System.out.println("this Thread name is :"+this.currentThread().getName()+"--"+count);
//}
}
}
ConThread th=new ConThread();
Thread th0=new Thread(th,"A");
Thread th1=new Thread(th,"B");
Thread th2=new Thread(th,"C");
th0.start();
th1.start();
th2.start();
4：currentThread
isAlive 判断线程是否存活状态，start 后
public static void main(String[] args) {
// TODO Auto-generated method stub
CountOperate c=new CountOperate();
Thread th0=new Thread(c,"A");
Thread th1=new Thread(c,"B");
// System.out.println("th0 id :"+th0.getId());
//System.out.println("main begain th0 is alive :"+th0.isAlive());
// th0.setName("A");
th0.start();
th1.start();
// System.out.println("th0 id :"+th0.getId());
// System.out.println("main begain th0 is alive :"+th0.isAlive());
public class CountOperate extends Thread {
public CountOperate() {
System.out.println("countOperate --begain");
System.out.println("Thread.currentThread.getName():"+Thread.currentThread().getName());
System.out.println("Thread.currentThread.isAlive:"+Thread.currentThread().isAlive());
System.out.println("this.isAlive:"+this.isAlive());
System.out.println("this.getName:"+this.getName());
System.out.println("countOperate --end");
}
@Override
public void run() {
// TODO Auto-generated method stub
super.run();
System.out.println("cunThread.getId:"+this.getId());
System.out.println("run --begain");
System.out.println("Thread.currentThread.getName():"+Thread.currentThread().getName()); // currentThread 是执行该代码块的线程
//System.out.println("Thread.currentThread.isAlive:"+Thread.currentThread().isAlive());
//System.out.println("this.isAlive:"+this.isAlive()); // 是false 搞不懂
//System.out.println("cunThread.getId:"+this.getId());
// this指当前的线程 CountOperate 该对象传入new Thread ，run 是new Thread 对象调用的 即是 由 A,B 调用
System.out.println("this.getName:"+this.getName());
System.out.println("run --end");
}
}
打印：
countOperate --begain
Thread.currentThread.getName():main
Thread.currentThread.isAlive:true
this.isAlive:false
this.getName:Thread-0
countOperate --end
cunThread.getId:10
run --begain
Thread.currentThread.getName():A
Thread.currentThread.isAlive:true
this.isAlive:false
cunThread.getId:10
this.getName:Thread-0
run --end
cunThread.getId:10
run --begain
Thread.currentThread.getName():B
Thread.currentThread.isAlive:true
this.isAlive:false
cunThread.getId:10
this.getName:Thread-0
run --end
5：Sleep()
在指定毫秒数内让当前"正在执行的线程"休眠，这个线程是指this.currentThread()返回的线程
public class SleepThread extends Thread{ @Override public void run() { // TODO Auto-generated method stub super.run(); try { System.err.println("run threadName = "+this.currentThread().getName()+" begain"); Thread.sleep(2000); System.err.println("run threadName = "+this.currentThread().getName()+" end"); } catch (InterruptedException e) { // TODO: handle exception } } } SleepThread th0=new SleepThread(); System.err.println("begain = "+System.currentTimeMillis()); th0.run(); System.err.println("end = "+System.currentTimeMillis());
输出：
begain = 1521465823061
run threadName = main begain
run threadName = main end
end = 1521465825073
th0.run 变成th0.start();
输出：
begain = 1521466181414
end = 1521466181414
run threadName = Thread-0 begain
run threadName = Thread-0 end
SleepThread th0=new SleepThread();
Thread th1=new Thread(th0);
Thread th2=new Thread(th0);
System.err.println("begain = "+System.currentTimeMillis());
th2.setName("A");
th2.start();
th1.setName("B");
th1.start();
System.err.println("end = "+System.currentTimeMillis());
begain = 1521466821288
end = 1521466821288
run threadName = A begain
run threadName = B begain
run threadName = A end
run threadName = B end // this.currentThread().getName() currentThread指执行该改代码块的线程 和this区别开来
6：interrupt() 中断线程
public class InterruptedThread extends Thread{
@Override
public void run() {
// TODO Auto-generated method stub
super.run();
for (int i = 0; i <1000; i++) {
System.out.println("i = "+(i+1));
}
}
}
public class ThreadTest {
public static void main(String[] args) {
// TODO Auto-generated method stub
try {
InterruptedThread th=new InterruptedThread();
th.start();
Thread.sleep(1000);
th.interrupt();
System.out.println("是否停止了1--"+th.interrupted());
System.out.println("是否停止了2--"+th.interrupted());
} catch (InterruptedException e) {
// TODO: handle exception
}
}
}
i = 999
i = 1000
是否停止了1--false //th.interrupt 是指main线程
是否停止了2--false
try {
InterruptedThread th=new InterruptedThread();
th.start();
Thread.sleep(1000);
Thread.currentThread().interrupt();
System.out.println("是否停止了1--"+Thread.currentThread().interrupted());
System.out.println("是否停止了2--"+Thread.currentThread().interrupted());
} catch (InterruptedException e) {
// TODO: handle exception
}
i = 999
i = 1000
是否停止了1--true
是否停止了2--false 这里是中端了main线程
但是俩次调用interrupted() interrupted() 判断当前线程是否处于中断状态，线程的中断状态由该方法清除
注意点：
isInterrupted()对比interrupted（）没有清除功能