java设计模式_单例模式

Design Pattern(设计模式)  经典的设计模式大概23个
单例模式(Singleton)：表示一个类只会生成唯一的一个对象


public class SingletonTest{
public static void main(String[] args){
SingleTon st1 = SingleTon.getInstance();
SingleTon st2 = SingleTon.getInstance();

st1.a = 10;
System.out.println( st1.a );
System.out.println( st2.a );
st2.a = 100;
System.out.println( st1.a );
System.out.println( st2.a );


}
}


class SingleTon{
int a;
private static SingleTon singleton;

private SingleTon(){

}


public static SingleTon getInstance(){
if(singleton == null){
singleton = new SingleTon();
}
return singleton;
}
}