饿汉式（立即加载）
package com.zuoyang.singleton;
/**
* 饿汉式：
* * 线程安全，在线程还出现以前就是创建了对象
*
*/
public class SingLetonHungry {
private static SingLetonHungry singLetonHungry = new SingLetonHungry();
private SingLetonHungry(){}
public static SingLetonHungry getInstance(){
return singLetonHungry;
}
}
线程类
package com.zuoyang.singleton;
public class SingLetonHungryThread extends Thread {
@Override
public void run(){
// 通过打印类的hashCode来确定是否为一个对象
System.out.println(SingLetonHungry.getInstance().hashCode());
}
}
运行类
package com.zuoyang.singleton;
public class SingLetonHungryRun {
public static void main(String[] args) {
SingLetonHungryThread singLetonHungryThread1 = new SingLetonHungryThread();
SingLetonHungryThread singLetonHungryThread2 = new SingLetonHungryThread();
SingLetonHungryThread singLetonHungryThread3 = new SingLetonHungryThread();
singLetonHungryThread1.start();
singLetonHungryThread2.start();
singLetonHungryThread3.start();
}
}
运行结果
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懒汉式（延迟加载）
线程不安全版
package com.zuoyang.singleton;
/**
* 懒汉式单例，但是多线程的情况下不安全
*/
public class SinLetonLazyOne {
//静态块，公共内存区域
private static SinLetonLazyOne sinLetonLazyOne;
private SinLetonLazyOne(){
}
//调用方法之前，先判断
//如果没有初始化，将其进行初始化,并且赋值
//将该实例缓存好
public static SinLetonLazyOne getInstance(){
if (sinLetonLazyOne!=null) {
}else {
//两个线程都会进入这个if里面
sinLetonLazyOne = new SinLetonLazyOne();
}
//如果已经初始化，直接返回之前已经保存好的结果
return sinLetonLazyOne;
}
}
线程类
package com.zuoyang.singleton;
public class SinLetonlLazyOneThread extends Thread {
@Override
public void run(){
System.out.println(SinLetonLazyOne.getInstance().hashCode());
}
}
运行类
package com.zuoyang.singleton;
public class SinLetonlLazyOneRun {
public static void main(String[] args) {
SinLetonlLazyOneThread sinLetonlLazyOneThread1 = new SinLetonlLazyOneThread();
SinLetonlLazyOneThread sinLetonlLazyOneThread2 = new SinLetonlLazyOneThread();
SinLetonlLazyOneThread sinLetonlLazyOneThread3 = new SinLetonlLazyOneThread();
sinLetonlLazyOneThread1.start();
sinLetonlLazyOneThread2.start();
sinLetonlLazyOneThread3.start();
}
}
运行结果
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synchronized关键字版
package com.zuoyang.singleton;
/**
* 基于加锁的线程安全的懒汉式单例
*/
public class SinLetonLazyTwo {
private static SinLetonLazyTwo sinLetonLazyTwo;
private SinLetonLazyTwo() {
}
//加锁 来保证多线程的情况下也是一个单例
synchronized public static SinLetonLazyTwo getInstance() {
try {
if (sinLetonLazyTwo != null) {
} else {
Thread.sleep(3000);
sinLetonLazyTwo = new SinLetonLazyTwo();
}
} catch (InterruptedException e) {
e.printStackTrace();
}
return sinLetonLazyTwo;
}
}
线程类
package com.zuoyang.singleton;
public class SinLetonlLazyTwoThread extends Thread {
@Override
public void run(){
System.out.println(SinLetonLazyTwo.getInstance().hashCode());
}
}
运行类
package com.zuoyang.singleton;
public class SinLetonlLazyTwoRun {
public static void main(String[] args) {
SinLetonlLazyTwoThread sinLetonlLazyTwoThread1 = new SinLetonlLazyTwoThread();
SinLetonlLazyTwoThread sinLetonlLazyTwoThread2 = new SinLetonlLazyTwoThread();
SinLetonlLazyTwoThread sinLetonlLazyTwoThread3 = new SinLetonlLazyTwoThread();
sinLetonlLazyTwoThread1.start();
sinLetonlLazyTwoThread2.start();
sinLetonlLazyTwoThread3.start();
}
}
运行结果
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同步代码块版（线程不安全）
package com.zuoyang.singleton;
/**
* 基于加锁的线程不安全的懒汉式单例
*/
public class SinLetonLazyTwoTwo {
private static SinLetonLazyTwoTwo sinLetonLazyTwoOne;
private SinLetonLazyTwoTwo() {
}
//加锁 来保证多线程的情况下也是一个单例
public static SinLetonLazyTwoTwo getInstance() {
try {
if (sinLetonLazyTwoOne != null) {
} else {
Thread.sleep(3000);
synchronized (SinLetonLazyTwoTwo.class) {
sinLetonLazyTwoOne = new SinLetonLazyTwoTwo();
}
}
} catch (InterruptedException e) {
e.printStackTrace();
}
return sinLetonLazyTwoOne;
}
}
线程类
package com.zuoyang.singleton;
public class SinLetonlLazyTwoOneThread extends Thread {
@Override
public void run(){
System.out.println(SinLetonLazyTwoOne.getInstance().hashCode());
}
}
运行类
package com.zuoyang.singleton;
public class SinLetonlLazyTwoTwoRun {
public static void main(String[] args) {
SinLetonlLazyTwoTwoThread sinLetonlLazyTwoTwoThread1 = new SinLetonlLazyTwoTwoThread();
SinLetonlLazyTwoTwoThread sinLetonlLazyTwoTwoThread2 = new SinLetonlLazyTwoTwoThread();
SinLetonlLazyTwoTwoThread sinLetonlLazyTwoTwoThread3 = new SinLetonlLazyTwoTwoThread();
sinLetonlLazyTwoTwoThread1.start();
sinLetonlLazyTwoTwoThread2.start();
sinLetonlLazyTwoTwoThread3.start();
}
}
运行结果
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DCL双检查锁机制版（Double-Check Locking）
package com.zuoyang.singleton;
/**
* 基于双重检查锁的机制实现的单例模式
*/
public class SinLetonLazyThree {
private static SinLetonLazyThree sinLetonLazyTwoOne;
private SinLetonLazyThree() {
}
public static SinLetonLazyThree getInstance() {
try {
//存在多个线程，跑进来在这里
if (sinLetonLazyTwoOne != null) {
} else {
Thread.sleep(3000);
//后面进来的线程需要判断lazy是否已经初始化了，不然的话，会重新创建新的对象
synchronized (SinLetonLazyThree.class) {
if (sinLetonLazyTwoOne == null)
sinLetonLazyTwoOne = new SinLetonLazyThree();
}
}
} catch (InterruptedException e) {
e.printStackTrace();
}
return sinLetonLazyTwoOne;
}
}
线程类
package com.zuoyang.singleton;
public class SinLetonlLazyThreeThread extends Thread {
@Override
public void run(){
System.out.println(SinLetonLazyThree.getInstance().hashCode());
}
}
运行类
package com.zuoyang.singleton;
public class SinLetonlLazyThreeRun {
public static void main(String[] args) {
SinLetonlLazyThreeThread sinLetonlLazyThreeThread1 = new SinLetonlLazyThreeThread();
SinLetonlLazyThreeThread sinLetonlLazyThreeThread2 = new SinLetonlLazyThreeThread();
SinLetonlLazyThreeThread sinLetonlLazyThreeThread3 = new SinLetonlLazyThreeThread();
sinLetonlLazyThreeThread1.start();
sinLetonlLazyThreeThread2.start();
sinLetonlLazyThreeThread3.start();
}
}
运行结果
[图片上传失败...(image-63ced0-1563808417878)]
使用静态内部类实现单例模式
package com.zuoyang.singleton;
public class SingLetonStatic {
private static SingLetonStatic singLetonStatic =null;
private SingLetonStatic(){}
static {
singLetonStatic = new SingLetonStatic();
}
public static SingLetonStatic getInstance() {
return singLetonStatic;
}
}
线程类
package com.zuoyang.singleton;
public class SingLetonStaticThread extends Thread{
@Override
public void run(){
for (int i = 0; i <5 ; i++) {
System.out.println(SingLetonStatic.getInstance().hashCode());
}
}
}
运行类
package com.zuoyang.singleton;
public class SingLetonStaticRun {
public static void main(String[] args) {
SingLetonStaticThread singLetonStaticThread1 = new SingLetonStaticThread();
SingLetonStaticThread singLetonStaticThread2 = new SingLetonStaticThread();
SingLetonStaticThread singLetonStaticThread3 = new SingLetonStaticThread();
singLetonStaticThread1.start();
singLetonStaticThread2.start();
singLetonStaticThread3.start();
}
}
运行结果
[图片上传失败...(image-15f231-1563808417878)]
序列化与反序列化的单例模式
package com.zuoyang.singleton;
import java.io.Serializable;
public class SingLetonSerializable implements Serializable {
private SingLetonSerializable(){}
private static class SingLetonSerializableHandler{
private static final SingLetonSerializable singLetonSerializable = new SingLetonSerializable();
}
public static SingLetonSerializable getInstance(){
return SingLetonSerializableHandler.singLetonSerializable;
}
protected Object readResolve(){
return SingLetonSerializableHandler.singLetonSerializable;
}
}
运行类
package com.zuoyang.singleton;
import java.io.*;
public class SingLetonSerializableSaveAndRead {
public static void main(String[] args) {
try {
SingLetonSerializable singLetonSerializable = SingLetonSerializable.getInstance();
FileOutputStream fileOutputStream = new FileOutputStream(new File("E://MyOne.txt"));
ObjectOutputStream objectOutputStream = new ObjectOutputStream(fileOutputStream);
objectOutputStream.writeObject(singLetonSerializable);
objectOutputStream.close();
fileOutputStream.close();
System.out.println(singLetonSerializable.hashCode());
}catch (FileNotFoundException e){
e.printStackTrace();
}catch (IOException e){
e.printStackTrace();
}
FileInputStream fileInputStream = null;
try {
fileInputStream = new FileInputStream(new File("E://MyOne.txt"));
ObjectInputStream objectInputStream = new ObjectInputStream(fileInputStream);
SingLetonSerializable singLetonSerializable = (SingLetonSerializable)objectInputStream.readObject();
objectInputStream.close();
fileInputStream.close();
System.out.println(singLetonSerializable.hashCode());
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
}
运行结果
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enum枚举实现单例模式
package com.zuoyang.singleton;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class SingLetonEumOne {
public enum SingLetonEumTest {
connectionFactory;
private Connection connection;
private SingLetonEumTest(){
try {
Class.forName("com.mysql.jdbc.Driver");
String url="jdbc:mysql://localhost:3306";
String user="root";
String password="root";
connection = DriverManager.getConnection(url,user,password);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
}
public Connection getConnection(){
return connection;
}
}
public static Connection getConnection(){
return SingLetonEumTest.connectionFactory.getConnection();
}
}
线程类
package com.zuoyang.singleton;
public class SingLetonEumThreadTest extends Thread {
@Override
public void run(){
for (int i = 0; i <5 ; i++) {
System.out.println(SingLetonEumOne.getConnection().hashCode());
}
}
}
运行类
package com.zuoyang.singleton;
public class SingLetonEumRunTest {
public static void main(String[] args) {
SingLetonEumThreadTest singLetonEumThreadTest1 = new SingLetonEumThreadTest();
SingLetonEumThreadTest singLetonEumThreadTest2 = new SingLetonEumThreadTest();
SingLetonEumThreadTest singLetonEumThreadTest3 = new SingLetonEumThreadTest();
singLetonEumThreadTest1.start();
singLetonEumThreadTest2.start();
singLetonEumThreadTest3.start();
}
}
运行结果
[图片上传失败...(image-70c9ae-1563808417878)]
GitHub地址
https://github.com/dxf1998/singleton.git
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