java 单例模式

public class DanLi {
    private DanLi()
    {
        
    }
    
    private  static DanLi d1=null;

    public static DanLi instance()
    {
        
        if(d1==null)
        {
            d1=new DanLi();
        }
        return d1;
    }
    private int m=0;
    public void run()
    {
        for(int i=0;i<10;i++)
        {
            m++;
            
            System.out.println("m="+m);
        }
        
    }
    public static void main(String[] args) {
        System.out.println("t1单例");
        DanLi t1=DanLi.instance();
        t1.run();
        System.out.println("t2单例");
        DanLi t2=DanLi.instance();
        t2.run();

    }

}

public class DanLi2 {
    private DanLi2()
    {
        
    }
    
    private final static DanLi2 t1=new DanLi2();
    
    
    public static DanLi2 instance()
    {
        
        return t1;
    }
    private int m=0;
    public void run()
    {
        for(int i=0;i<10;i++)
        {
            m++;
            
            System.out.println("m="+m);
        }
        
    }
    public static void main(String[] args) {
        System.out.println("t1单例");
        DanLi t1=DanLi.instance();
        t1.run();
        System.out.println("t2单例");
        DanLi t2=DanLi.instance();
        t2.run();

    }

}