单例模式(Singleton Pattern)

 单例模式确保一个类只有一个实例，并提供一个全局访问点。 

1：饥汉式

public class Singleton {

//私有构造方法
private Singleton() {}
//提供静态变量
private static Singleton singleton;
//提供共有访问方法
public static Singleton getIntances() {
if(singleton == null) {
singleton = new Singleton();
}
return singleton;
}

}

 

 

2：饿汉式

public class Singleton {

private Singleton() {}

private static Singleton singleton = new Singleton();

public static Singleton getIntances() {
return singleton;
}
}

 

3：多线程下的Singleton
public class Singleton {

private Singleton() {}

private static Singleton singleton;

public static synchronized Singleton getIntances() {
if(singleton == null) {
singleton = new Singleton();
}
return singleton;
}
}