1 线程的两类java声明实现方式
A 继承Thread
B 实现runnable
例子
public class TestThread1 {
public static void main(String args[]) {
Runner1 r = new Runner1();
r.start();
//Thread t = new Thread(r);
//t.start();
for(int i=0; i<100; i++) {
System.out.println("Main Thread:------" + i);
}
}
}
//class Runner1 implements Runnable {
class Runner1 extends Thread {
public void run() {
for(int i=0; i<100; i++) {
System.out.println("Runner1 :" + i);
}
}
}
2 sleep用法
import java.util.*;
public class TestSleep {
public static void main(String[] args) {
MyThread thread = new MyThread();
thread.start();
try {Thread.sleep(10000);}
catch (InterruptedException e) {}
thread.interrupt();
}
}
class MyThread extends Thread {
boolean flag = true;
public void run(){
while(flag){
System.out.println("==="+new Date()+"===");
try {
sleep(1000);
} catch (InterruptedException e) {
return;
}
}
}
}
3 join:等子线程执行完后，主线程再执行
public class TestJoin {
public static void main(String[] args) {
MyThread2 t1 = new MyThread2("abcde");
t1.start();
try {
t1.join();
} catch (InterruptedException e) {}
for(int i=1;i<=10;i++){
System.out.println("i am main thread");
}
}
}
class MyThread2 extends Thread {
MyThread2(String s){
super(s);
}
public void run(){
for(int i =1;i<=10;i++){
System.out.println("i am "+getName());
try {
sleep(1000);
} catch (InterruptedException e) {
return;
}
}
}
}
4 yield(),让出线程给其他
public class TestYield {
public static void main(String[] args) {
MyThread3 t1 = new MyThread3("t1");
MyThread3 t2 = new MyThread3("t2");
t1.start(); t2.start();
}
}
class MyThread3 extends Thread {
MyThread3(String s){super(s);}
public void run(){
for(int i =1;i<=100;i++){
System.out.println(getName()+": "+i);
if(i%10==0){
yield();
}
}
}
5 线程优先级
public class TestPriority {
public static void main(String[] args) {
Thread t1 = new Thread(new T1());
Thread t2 = new Thread(new T2());
t1.setPriority(Thread.NORM_PRIORITY + 3);
t1.start();
t2.start();
}
}
class T1 implements Runnable {
public void run() {
for(int i=0; i<1000; i++) {
System.out.println("T1: " + i);
}
}
}
class T2 implements Runnable {
public void run() {
for(int i=0; i<1000; i++) {
System.out.println("------T2: " + i);
}
}
}
6 线程的synchronized.
public class TestSync implements Runnable {
Timer timer = new Timer();
public static void main(String[] args) {
TestSync test = new TestSync();
Thread t1 = new Thread(test);
Thread t2 = new Thread(test);
t1.setName("t1");
t2.setName("t2");
t1.start();
t2.start();
}
public void run(){
timer.add(Thread.currentThread().getName());
}
}
class Timer{
private static int num = 0;
public synchronized void add(String name){
//synchronized (this) {
num ++;
try {Thread.sleep(1);}
catch (InterruptedException e) {}
System.out.println(name+", 你是第"+num+"个使用timer的线程");
//}
}
}
注意，这里由于t1,t2两个线程，都会同时使用到公共资源区timer，因此会发生不同步的问题，必须要加上synchronized
7 死锁的例子
public class TestDeadLock implements Runnable {
public int flag = 1;
static Object o1 = new Object(), o2 = new Object();
public void run() {
System.out.println("flag=" + flag);
if(flag == 1) {
synchronized(o1) {
try {
Thread.sleep(500);
} catch (Exception e) {
e.printStackTrace();
}
synchronized(o2) {
System.out.println("1");
}
}
}
if(flag == 0) {
synchronized(o2) {
try {
Thread.sleep(500);
} catch (Exception e) {
e.printStackTrace();
}
synchronized(o1) {
System.out.println("0");
}
}
}
}
public static void main(String[] args) {
TestDeadLock td1 = new TestDeadLock();
TestDeadLock td2 = new TestDeadLock();
td1.flag = 1;
td2.flag = 0;
Thread t1 = new Thread(td1);
Thread t2 = new Thread(td2);
t1.start();
t2.start();
}
}
8 要注意的，比如如下程序
public class Sync implements Runnable {
int b = 100;
public synchronized void m1() throws Exception{
//Thread.sleep(2000);
b = 1000;
Thread.sleep(5000);
System.out.println("b = " + b);
}
public synchronized void m2() throws Exception {
Thread.sleep(2500);
b = 2000;
}
public void run() {
try {
m1();
} catch(Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) throws Exception {
Sync tt = new Sync();
Thread t = new Thread(tt);
t.start();
tt.m2();
System.out.println(tt.b);
}
}
输出：1000
b=1000
因为启动m2后，获得锁，之后释放后，由m1来执行，最后b=1000.
如果public void m2() throws Exception {
则b=2000了，一直都是b=2000最后
9 生产者，消费者问题
public class ProducerConsumer {
public static void main(String[] args) {
SyncStack ss = new SyncStack();
Producer p = new Producer(ss);
Consumer c = new Consumer(ss);
new Thread(p).start();
new Thread(p).start();
new Thread(p).start();
new Thread(c).start();
}
}
class WoTou {
int id;
WoTou(int id) {
this.id = id;
}
public String toString() {
return "WoTou : " + id;
}
}
class SyncStack {
int index = 0;
WoTou[] arrWT = new WoTou[6];
public synchronized void push(WoTou wt) {
while(index == arrWT.length) {
try {
this.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
this.notifyAll();
arrWT[index] = wt;
index ++;
}
public synchronized WoTou pop() {
while(index == 0) {
try {
this.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
this.notifyAll();
index--;
return arrWT[index];
}
}
class Producer implements Runnable {
SyncStack ss = null;
Producer(SyncStack ss) {
this.ss = ss;
}
public void run() {
for(int i=0; i<20; i++) {
WoTou wt = new WoTou(i);
ss.push(wt);
System.out.println("生产了：" + wt);
try {
Thread.sleep((int)(Math.random() * 200));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
class Consumer implements Runnable {
SyncStack ss = null;
Consumer(SyncStack ss) {
this.ss = ss;
}
public void run() {
for(int i=0; i<20; i++) {
WoTou wt = ss.pop();
System.out.println("消费了: " + wt);
try {
Thread.sleep((int)(Math.random() * 1000));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
