把synchronized当作函数修饰符时，示例代码如下:
Public synchronized void method(){
//….
}
这也就是同步方法，那这时synchronized锁定的是哪个对象呢？他锁定的是调用这个同步方法对象。也就是说，当一个对象P1在不同的线程中执行这个同步方法时，他们之间会形成互斥，达到同步的效果。但是这个对象所属的Class所产生的另一对象P2却能够任意调用这个被加了synchronized关键字的方法。
如同这样
public void method()
{
synchronized (this) // (1)
{
//…..
}
}
此处的this指的是什么呢？他指的就是调用这个方法的对象，如P1。可见同步方法实质是将synchronized作用于object reference。――那个拿到了P1对象锁的线程，才能够调用P1的同步方法，而对P2而言，P1这个锁和他毫不相干，程式也可能在这种情形下摆脱同步机制的控制，造成数据混乱。具体使用像这样:
package com.java.Thread;
public class Mysynchronized {
/**
* @param args
*/
public static void main(String[] args) {
/*
* GetTickets gt1 = new GetTickets(); GetTickets gt2 = new GetTickets();
* GetTickets gt3 = new GetTickets(); gt1.setName("窗口一");
* gt2.setName("窗口二"); gt3.setName("窗口三"); gt1.start(); gt2.start();
* gt3.start();
*/
GetTickets2 gt = new GetTickets2();
Thread th1 = new Thread(gt, "窗口一");
Thread th2 = new Thread(gt, "窗口二");
Thread th3 = new Thread(gt, "窗口三");
th1.start();
try {
Thread.sleep(500);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
gt.flag = true;
th2.start();
th3.start();
}
}
class GetTickets2 implements Runnable {
private int tickets = 10;
boolean flag = false;
/* Object ob = new Object();*/
public void run() {
if (flag) {
for (int i = 0; i < 10; i++) {
//synchronized (ob) {//如果用ob就无法同步
synchronized (this) {
if (tickets > 0) {
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName()
+ "卖出" + (tickets--) + "号票"+":同步代码块");
}
}
}
} else {
for (int i = 0; i < 10; i++) {
function();
}
}
}
public synchronized void function() {
if (tickets > 0) {
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName() + "卖出"
+ (tickets--) + "号票"+"：同步函数");
}
}
}
/*
* class GetTickets extends Thread{ //private static int tickets = 10; private
* int tickets = 10; public void run(){
*
* for (int i = 0; i < 10; i++) { if(tickets>0){
* System.out.println(Thread.currentThread().getName()+"卖出"+(tickets--)+"号票"); }
* } } }
*/
将synchronized作用于static 函数 同步的锁就是它自己本身的字节码，示例代码如下：
Class Foo
{
public synchronized static void method1() // 同步的static 函数
{
//….
}
public void method2()
{
synchronized(Foo.class) // class literal(类名称字面常量)
}
}
具体代码如下
package cn.java.thread;
/*
证明同步函数用的是this这把锁
*/
public class Tickets1 {
/**
* @param args
*/
public static void main(String[] args) {
/*
* GetTickets gt1 = new GetTickets(); GetTickets gt2 = new GetTickets();
* GetTickets gt3 = new GetTickets(); gt1.setName("窗口一");
* gt2.setName("窗口二"); gt3.setName("窗口三"); gt1.start(); gt2.start();
* gt3.start();
*/
GetTickets2 gt = new GetTickets2();
Thread th1 = new Thread(gt, "窗口一");
Thread th2 = new Thread(gt, "窗口二");
Thread th3 = new Thread(gt, "窗口三");
th1.start();
try {
Thread.sleep(500);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
gt.flag = true;
th2.start();
th3.start();
}
}
class GetTickets2 implements Runnable {
private static int tickets = 10;
boolean flag = false;
Object ob = new Object();
public void run() {
if (flag) {
for (int i = 0; i < 10; i++) {
//synchronized (this.getClass()) {
synchronized (GetTickets2.class) {
if (tickets > 0) {
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName()
+ "卖出" + (tickets--) + "号票"+":同步代码块");
}
}
}
} else {
for (int i = 0; i < 10; i++) {
function();
}
}
}
public static synchronized void function() {
if (tickets > 0) {
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName() + "卖出"
+ (tickets--) + "号票"+"：同步函数");
}
}
}
/*
* class GetTickets extends Thread{ //private static int tickets = 10; private
* int tickets = 10; public void run(){
*
* for (int i = 0; i < 10; i++) { if(tickets>0){
* System.out.println(Thread.currentThread().getName()+"卖出"+(tickets--)+"号票"); }
* } } }
*/
然后嘞是 wait notify notifyall 这三个(两个)方法的 理解了 第一步 wait的作用是阻塞 notify的作用是唤醒
讲这个 要用到以前学到的生产者和消费者 对于他们的理解:
1.这些方法都存在与同步中
2;使用这些方法时必须要标记所属的同步锁
3:锁可以是任意对象,所以任意对象调用的方法一定定义在object类中 废话不多上代码:
这是同步代码块的
package com.java.Thread;
//定义一个rbq
class Production{
private String name;
private String country;
private boolean flag = true;
public boolean isFlag() {
return flag;
}
public void setFlag(boolean flag) {
this.flag = flag;
}
public String getCountry() {
return country;
}
public void setCountry(String country) {
this.country = country;
}
public void setName(String name) {
this.name = name;
}
public String getName() {
return name;
}
}
class Producer implements Runnable{
private Production p = null;
public Producer(Production p) {
this.p = p;
}
public void run(){
boolean b = true;
while(true){
synchronized (p) {
if(p.isFlag()){
//这个b就是打酱油的
if(b){
p.setName("李小文院士");
p.setCountry("中国");
b = false;
}
else{
p.setName("加来道雄博士");
p.setCountry("日本");
b = true;
}
//唤醒 并且这里注意 把flag改变成了 false
p.setFlag(false);
p.notify();
}
else
try {
//老样子 否则就过来阻塞
p.wait();
} catch (Exception e) {
// TODO: handle exception
}
}
}
}
}
class Saler implements Runnable{
private Production p = null;
//表明同步的锁!!!!
public Saler(Production p) {
this.p = p;
}
public void run() {
while(true){
synchronized (p) {
//上面的 isFlage被设定成 false了 所以这里要不等于 然后他们 就这样一直轮回下去 下面没了就让上面造
if(!p.isFlag()){
//获取前面的 赋值
System.out.println(p.getName()+":"+p.getCountry());
p.setFlag(true);
//唤醒 动起来
p.notify();
}
else{
try {
//阻塞
p.wait();
} catch (Exception e) {
// TODO: handle exception
}
}
}
}
}
}
public class ProductionDemo{
public static void main(String[] args) {
Production p = new Production();
Producer producer = new Producer(p);
Saler saler = new Saler(p);
Thread th1 = new Thread(producer);
Thread th2 = new Thread(saler);
th1.start();
th2.start();
}
}
小钢炮这个是同步函数的
public class ProductionDemo{
public static void main(String[] args) {
// 这是同步函数的
/* Production p = new Production();
Producer producer = new Producer(p);
Saler saler = new Saler(p);
Thread th1 = new Thread(producer);
Thread th2 = new Thread(saler);
th1.start();
th2.start();
*/
//同步代码块
Production p = new Production();
Producer pd = new Producer(p);
Saler s = new Saler(p);
Thread th1 = new Thread(pd);
Thread th2 = new Thread(s);
th1.start();
th2.start();
}
}
//同步代码块
class Production {
private String name;
private int num = 0;
private boolean b = false;
public boolean isB() {
return b;
}
public void setB(boolean b) {
this.b = b;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getNum() {
return num;
}
public void setNum(int num) {
this.num = num;
}
}
class Producer implements Runnable {
private Production p = null;
public Producer(Production p) {
this.p = p;
}
public void run() {
while (true) {
synchronized (p) {
if (p.isB()) {
try {
p.wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
p.setName("小钢炮");
p.setNum(p.getNum() + 1);
System.out.println("生产：" + p.getName() + p.getNum());
p.setB(true);
p.notify();
}
}
}
}
class Saler implements Runnable {
private Production p = null;
//获取定义的锁要一样
public Saler(Production p) {
this.p = p;
}
public void run() {
while (true) {
synchronized (p) {
if (!p.isB()) {
try {
//阻塞
p.wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
System.out.println("卖：" + p.getName() + p.getNum());
p.setB(false);
//唤醒
p.notify();
}
}
}
}
然后了是多生产者和多消费者 嘿嘿上码:
package cn.java.thread1;
public class ProductionDemo2 {
/**
* @param args
*/
public static void main(String[] args) {
Production2 p = new Production2();
Producer2 pd = new Producer2(p);
Saler2 s = new Saler2(p);
Thread th1 = new Thread(pd);
Thread th2 = new Thread(pd);
Thread th3 = new Thread(s);
Thread th4 = new Thread(s);
Thread th5 = new Thread(pd);
Thread th6 = new Thread(s);
th1.start();
th2.start();
th3.start();
th4.start();
th5.start();
th6.start();
}
}
class Production2 {
private String name;
private int num = 0;
private boolean b = false;
public boolean isB() {
return b;
}
public void setB(boolean b) {
this.b = b;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getNum() {
return num;
}
public void setNum(int num) {
this.num = num;
}
public synchronized void produce() {
//if (b) {
while (b) {
try {
this.wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
setName("小钢炮");
setNum(getNum() + 1);
System.out.println("生产：" + getName() + getNum());
setB(true);
//notify();
notifyAll();
}
public synchronized void sale() {
//if (!b) {
while(!b){
try {
this.wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
System.out.println("卖：" + getName() + getNum());
setB(false);
//notify();
notifyAll();
}
}
class Producer2 implements Runnable {
private Production2 p = null;
public Producer2(Production2 p2) {
this.p = p2;
}
public void run() {
for (int i = 0; i < 100; i++) {
p.produce();
}
}
}
class Saler2 implements Runnable {
private Production2 p = null;
public Saler2(Production2 p2) {
this.p = p2;
}
public void run() {
for (int i = 0; i < 100; i++) {
p.sale();
}
}
}