设计模式一 单例模式(Singleton Pattern)

public class SingletonPattern {

private static final SingletonPattern singletonPattern= new SingletonPattern();

//限制住不能直接产生一个实例
private SingletonPattern(){
}

public synchronized static SingletonPattern getInstance(){
return singletonPattern;
}

}

此代码为线程安全类型

 

public class SingletonPattern {
private static SingletonPattern singletonPattern= null;
//限制住不能直接产生一个实例
private SingletonPattern(){
}
public SingletonPattern getInstance(){
if(this.singletonPattern == null){ //如果还没有实例，则创建一个
this.singletonPattern = new SingletonPattern();
}
return this.singletonPattern;
}
}

 此代码线程不安全