java 单例模式简单用例

Single.java(实现单例类):

class Single //单例模式示例

{

private static Single newSingle=null;

public int a=0;

private Single()//将构造函数设置为private,这样就不能在外部实例化本类，但还是可以在内部实例化

{

}

public static Single getSingle()//提供外部接口

{

if(newSingle==null)

newSingle=new Single();

return newSingle;

}

}

UseSingle.java:(用于测试)

class UseSingle
{
public static void main(String[] args)
{
Single newSingle=Single.getSingle();
System.out.println(newSingle.a);
newSingle.a=1;
System.out.println(newSingle.a);

Single single2=Single.getSingle();
single2.a=2;
System.out.println(newSingle.a);

}
}