java多线程创建
/**
* 实现Runnable接口的类
*
* @author leizhimin 2008-9-13 18:12:10
*/
public class DoSomething implements Runnable {
private String name;
public DoSomething(String name) {
this.name = name;
}
public void run() {
for (int i = 0; i < 5; i++) {
for (long k = 0; k < 100000000; k++) ;
System.out.println(name + ": " + i);
}
}
}
public class MyRunnable implements Runnable {
private Foo foo = new Foo();
public static void main(String[] args) {
MyRunnable r = new MyRunnable();
Thread ta = new Thread(r, "Thread-A");
Thread tb = new Thread(r, "Thread-B");
ta.start();
tb.start();
}
public void run() {
for (int i = 0; i < 3; i++) {
this.fix(30);
try {
Thread.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName() + " : 当前foo对象的x值= " + foo.getX());
}
}
public int fix(int y) {
return foo.fix(y);
}
}
线程锁
public int fix(int y) {
synchronized (this) {
x = x - y;
}
return x;
}
public synchronized int getX() {
return x++;
}
wait()、notify()、notifyAll()方法。
/**
* 计算输出其他线程锁计算的数据
*
* @author leizhimin 2008-9-15 13:20:38
*/
public class ThreadA {
public static void main(String[] args) {
ThreadB b = new ThreadB();
//启动计算线程
b.start();
//线程A拥有b对象上的锁。线程为了调用wait()或notify()方法，该线程必须是那个对象锁的拥有者
synchronized (b) {
try {
System.out.println("等待对象b完成计算。。。");
//当前线程A等待
b.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("b对象计算的总和是：" + b.total);
}
}
}
/**
* 计算1+2+3 ... +100的和
*
* @author leizhimin 2008-9-15 13:20:49
*/
public class ThreadB extends Thread {
int total;
public void run() {
synchronized (this) {
for (int i = 0; i < 101; i++) {
total += i;
}
//（完成计算了）唤醒在此对象监视器上等待的单个线程，在本例中线程A被唤醒
notify();
}
}
}
sleep
/**
* Java线程：线程的调度-休眠
*
* @author leizhimin 2009-11-4 9:02:40
*/
public class Test {
public static void main(String[] args) {
Thread t1 = new MyThread1();
Thread t2 = new Thread(new MyRunnable());
t1.start();
t2.start();
}
}
class MyThread1 extends Thread {
public void run() {
for (int i = 0; i < 3; i++) {
System.out.println("线程1第" + i + "次执行！");
try {
Thread.sleep(50);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
class MyRunnable implements Runnable {
public void run() {
for (int i = 0; i < 3; i++) {
System.out.println("线程2第" + i + "次执行！");
try {
Thread.sleep(50);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
线程的让步使用Thread.yield()方法，yield() 为静态方法，功能是暂停当前正在执行的线程对象，并执行其他线程。
join
/**
* Java线程：线程的调度-合并
*
* @author leizhimin 2009-11-4 9:02:40
*/
public class Test {
public static void main(String[] args) {
Thread t1 = new MyThread1();
t1.start();
for (int i = 0; i < 20; i++) {
System.out.println("主线程第" + i + "次执行！");
if (i > 2) try {
//t1线程合并到主线程中，主线程停止执行过程，转而执行t1线程，直到t1执行完毕后继续。
t1.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
class MyThread1 extends Thread {
public void run() {
for (int i = 0; i < 10; i++) {
System.out.println("线程1第" + i + "次执行！");
}
}
}
在使用synchronized关键字时候，应该尽可能避免在synchronized方法或synchronized块中使用sleep或者yield方法，因为synchronized程序块占有着对象锁，你休息那么其他的线程只能一边等着你醒来执行完了才能执行。不但严重影响效率，也不合逻辑。
同样，在同步程序块内调用yeild方法让出CPU资源也没有意义，因为你占用着锁，其他互斥线程还是无法访问同步程序块。当然与同步程序块无关的线程可以获得更多的执行时间。
/**
* Java线程：并发协作-生产者消费者模型
*
* @author leizhimin 2009-11-4 14:54:36
*/
public class Test {
public static void main(String[] args) {
Godown godown = new Godown(30);
Consumer c1 = new Consumer(50, godown);
Consumer c2 = new Consumer(20, godown);
Consumer c3 = new Consumer(30, godown);
Producer p1 = new Producer(10, godown);
Producer p2 = new Producer(10, godown);
Producer p3 = new Producer(10, godown);
Producer p4 = new Producer(10, godown);
Producer p5 = new Producer(10, godown);
Producer p6 = new Producer(10, godown);
Producer p7 = new Producer(80, godown);
c1.start();
c2.start();
c3.start();
p1.start();
p2.start();
p3.start();
p4.start();
p5.start();
p6.start();
p7.start();
}
}
/**
* 仓库
*/
class Godown {
public static final int max_size = 100; //最大库存量
public int curnum; //当前库存量
Godown() {
}
Godown(int curnum) {
this.curnum = curnum;
}
/**
* 生产指定数量的产品
*
* @param neednum
*/
public synchronized void produce(int neednum) {
//测试是否需要生产
while (neednum + curnum > max_size) {
System.out.println("要生产的产品数量" + neednum + "超过剩余库存量" + (max_size - curnum) + "，暂时不能执行生产任务!");
try {
//当前的生产线程等待
wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
//满足生产条件，则进行生产，这里简单的更改当前库存量
curnum += neednum;
System.out.println("已经生产了" + neednum + "个产品，现仓储量为" + curnum);
//唤醒在此对象监视器上等待的所有线程
notifyAll();
}
/**
* 消费指定数量的产品
*
* @param neednum
*/
public synchronized void consume(int neednum) {
//测试是否可消费
while (curnum < neednum) {
try {
//当前的生产线程等待
wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
//满足消费条件，则进行消费，这里简单的更改当前库存量
curnum -= neednum;
System.out.println("已经消费了" + neednum + "个产品，现仓储量为" + curnum);
//唤醒在此对象监视器上等待的所有线程
notifyAll();
}
}
/**
* 生产者
*/
class Producer extends Thread {
private int neednum; //生产产品的数量
private Godown godown; //仓库
Producer(int neednum, Godown godown) {
this.neednum = neednum;
this.godown = godown;
}
public void run() {
//生产指定数量的产品
godown.produce(neednum);
}
}
/**
* 消费者
*/
class Consumer extends Thread {
private int neednum; //生产产品的数量
private Godown godown; //仓库
Consumer(int neednum, Godown godown) {
this.neednum = neednum;
this.godown = godown;
}
public void run() {
//消费指定数量的产品
godown.consume(neednum);
}
}
