substring 的菜鸟问题

Question

String temp="\tghi";
        String temp1=temp.substring(0,0);
        String temp2=temp.substring(0,1); //watch是"\t"
        System.out.println(temp1.length());//输出是0
        System.out.println(temp2.length());//输出1
        
        if (temp1=="")
        {
            System.out.println("here");
        }
        else
        {
            System.out.println("there");//执行这条语句
        }        if (temp2=="")
       {
           System.out.println("Null");
       }
       else
       {
           System.out.println("NOt Null");//执行这条语句
       }请问这是为什么啊？谢谢

Answer 1

后面的贴错了          if  (temp2=="\t")  
             {  
                     System.out.println("Null");  
             }  
             else  
             {  
                     System.out.println("NOt  Null");//执行这条语句  
             }