java之对象引用static变量

如下面代码



Java代码
public class Test  
{  
    public static int a = 2;  
      
    public static void main(String[] args)  
    {  
        Test t = new Test();  
          
        t = null;  
          
        System.out.println(t.a);  
    }  
} 

public class Test
{
public static int a = 2;

public static void main(String[] args)
{
Test t = new Test();

t = null;

System.out.println(t.a);
}
}



输出为：



Java代码
2 

2



下面的代码

Java代码
public class Test  
{  
    public static int a = 2;  
    public int b = 3;  
      
    public static void main(String[] args)  
    {  
        Test t = new Test();  
          
        t = null;  
          
        System.out.println(t.a);  
        System.out.println(t.b);  
    }  
} 

public class Test
{
public static int a = 2;
public int b = 3;

public static void main(String[] args)
{
Test t = new Test();

t = null;

System.out.println(t.a);
System.out.println(t.b);
}
}



输出为：

Java代码
2 
Exception in thread "main" java.lang.NullPointerException 

2
Exception in thread "main" java.lang.NullPointerException



再看下面的代码：



Java代码
public class Test  
{  
    public int a = 3;  
    public static int b = 2;  
      
    public static void main(String[] args)  
    {  
        Test t = new Test();  
          
        t = null;  
          
        System.out.println(t.a);  
        System.out.println(t.b);  
    }  
} 

public class Test
{
public int a = 3;
public static int b = 2;

public static void main(String[] args)
{
Test t = new Test();

t = null;

System.out.println(t.a);
System.out.println(t.b);
}
}



输出为：



Java代码
Exception in thread "main" java.lang.NullPointerException 

Exception in thread "main" java.lang.NullPointerException