自动装箱时，存在缓存变量

public class Test 
{ 
    public  static void main(String[] args)
    {  
        //自动装箱的过程中,如果是一个字节大小数字,即-128~127,那么JVM会将其缓存起来
         Integer num1 = 5;
        Integer num2 = 5;
        Integer num3 = 6;
        System.out.println(num1 == num2);  //true
        System.out.println(num1 == num3);  //false
        
        num1 = -128;
        num2 = -128;
        System.out.println(num1 == num2);//true
        
        num1 = 128;
        num2 = 128;
        System.out.println(num1 == num2);//false
        
    } 
}