Java中Class.this和this的区别

在Java中， Class.this 和 this 可能指代相同或不同的对象，具体取决于用法。

这

this is a reference variable that refers to the current object. If there is ambiguity between the instance variables and parameters, this keyword resolves the problem of ambiguity.

类.this

Class.this is a reference variable that refers to the outer class object inside a nested class or anonymous methods. If there is ambiguity between the inner (or anonymous) class and outer class, Class.this resolves the problem of ambiguity.

如果没有嵌套（或匿名）类，则 this 和Class.this引用同一个对象。

示例代码

考虑下面给出的代码，其中 this 和 Class.this 都指向同一个对象。

Java

class Outer
{
    public void showOuter()
    {
          System.out.println ("this = " + this);
        System.out.println ("Outer.this = " + Outer.this);
    }
    
    public static void main (String[] args) 
    {
        Outer outer = new Outer();
        outer.showOuter();
    }
}

输出

this = Outer@b4c966a
Outer.this = Outer@b4c966a

在下面给出的代码中，添加了一个内部嵌套类。在这个例子中， this 和 Outer.this 指向不同的对象。

Java

class Outer
{
      class Inner
    {
        public void showOuter()
        {
            System.out.println ("Outer.this = " + Outer.this);
        }
        
        public void showInner()
        {
              System.out.println ("this = " + this);
        }
    }
    
    public static void main (String[] args) 
    {
        Outer outer = new Outer();
        Inner inner = outer.new Inner();
          
          inner.showOuter();
         inner.showInner();     
    }
}

输出

Outer.this = Outer@2f4d3709
this = Outer$Inner@4e50df2e

在下面给出的代码中，已经演示了 class.this 在匿名方法中的用法。在这个例子中，class.this 和 this 也指向不同的对象。出于演示的目的，使用了 JButton 并调用了它的 doClick() 方法。

Java

import javax.swing.JButton;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
  
class GFG
{
      public void createAndFireButton()
    {
         JButton button = new JButton();
        
           button.addActionListener(new ActionListener(){
            @Override
            public void actionPerformed(ActionEvent e)
            {
                System.out.println ("GFG.this = " + GFG.this);
                System.out.println ("this = " + this);
            }
        });
  
        button.doClick();
    }
    
       public static void main(String[] args)
    {    
          GFG gfg = new GFG();
        gfg.createAndFireButton();
    }
}

输出

GFG.this = GFG@1fbc7afb
this = GFG$1@45c8e616

Note: Please note that when using lambda expressions, class.this and this both refer to the same outer class reference. 

在下面给出的示例中，我们没有使用匿名类，而是使用 lambda 向 JButton 添加动作侦听器。

Java

import javax.swing.JButton;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
  
class GFG
{
      public void createAndFireButton()
    {
         JButton button = new JButton();
  
            button.addActionListener(e -> {
                  System.out.println ("GFG.this = " + GFG.this);
                System.out.println ("this = " + this);
            });
  
            button.doClick();
    }
    
       public static void main(String[] args)
    {    
          GFG gfg = new GFG();
        gfg.createAndFireButton();
    }
}

输出

GFG.this = GFG@1fbc7afb
this = GFG@1fbc7afb