Integer中equals和==简介说明

equals和==简介

equals:
    比较两个值是否相等

==：
    比较两个内存地址是否相等

 
  //情景1
   Integer c = 128;
   Integer d = 128;
   System.out.println(c == d);//false

   //情景2
   Integer a = 1;
   Integer b = 1;
   System.out.println(a == b);//true。b.intValue()

   //情景3
   Integer e = new Integer(1);
   Integer f =  new Integer(1);
   System.out.println(e == f);//false


       //情景4
   Integer e = new Integer(1);
   Integer f =  new Integer(1);
   System.out.println(e.equals(f));//true
 

valueOf方法说明

 public static Integer valueOf(int i) {
    //-128 到 127 从缓存中获取
      if (i >= IntegerCache.low && i <= IntegerCache.high)
          return IntegerCache.cache[i + (-IntegerCache.low)];
      return new Integer(i);
  }