整数a = 5和new Integer(5)有什么区别? [英] what is difference between integer a = 5 and new Integer(5)?
问题描述
如果我写下面的代码(在java中):
if i write below code(in java):
Integer a =new Integer(5);
Integer b=new Integer(5);
if(a==b){
System.out.println("In ==");
}
if(a.equals(b)){
System.out.println("In equals");
}
我的输出是:等于
但是如果我改变了第一行和第二行到 - >
My output is: "In equals" But if i change first and second line to ->
Integer a =5;
Integer b=5;
然后我的o / p是:
then my o/p is:
In ==
In equals
那又怎样创建一个Integer对象有区别吗?当我们这样做时如何创建整数a = 5
?
So what is difference in creating a Integer object? How it gets created when we do Integer a =5
?
这是否意味着a和b对象引用相同的对象,如果我创建整数a = 5
并创建另一个对象整数b = 5
?
Does it mean that a and b object refer to same object, if i create Integer a=5
and creates another object Integer b=5
?
推荐答案
整数a = 5
;被称为自动装箱,编译器将此表达式转换为实际的
Integer a = 5
; is called autoboxing, compiler converts this expression into actual
Integer a = Integer.valueOf(5);
对于小数字,默认为-128到127,Integer.valueOf(int)不会创建新的Integer实例,但从其缓存中返回一个值。所以这里
For small numbers, by default -128 to 127, Integer.valueOf(int) does not create a new instance of Integer but returns a value from its cache. So here
Integer a = 5;
Integer b= 5;
a
和 b
指向同一个对象, a == b
是 true
。
a
and b
point to the same Object and a == b
is true
.
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