int和Integer比较详解

先看代码

        @Test
    public void testEquals() {
        int int1 = 12;
        int int2 = 12;
        
        Integer integer1 = new Integer(12);
        Integer integer2 = new Integer(12);
        Integer integer3 = new Integer(127);
        
        Integer a1 = 127;
        Integer a2 = 127;
        
        Integer a = 128;
        Integer b = 128;
            
        System.out.println("int1 == int2 -> " + (int1 == int2));  //true                    
        System.out.println("int1 == integer1 -> " + (int1 == integer1));  //true            
        System.out.println("integer1 == integer2 -> " + (integer1 == integer2));     //false
        System.out.println("integer3 == a1 -> " + (integer3 == a1));    //false
        System.out.println("a1 == a2 -> " + (a1 == a2)); //true                            
        System.out.println("a == b -> " + (a == b));//false                                                    
    }   

1. 首先int1=int2不需要解释了
2. int1==integer1是因为Integer与int比较时会自动拆箱成int。这里的Integer不管是直接赋值还是new出来的对象。只要是和int比较都会自动拆箱。
3. integer1和integer2两者都是对象，不会拆箱。所以不相等