What is the need of an intValue() method if wrappers use unboxing?

问题

For example, look at this code:

Integer myInt = new Integer(5);
int i1 = myInt.intValue();
int i2 = myInt;

System.out.println(i1);
System.out.println(i2);

As you can see, I have two ways of copying my integer value from the wrapper to the primive:

I can use unboxing

OR

I can use the method intValue()

So... what's the need of having a method when there is already unboxing?

回答1:

Unboxing was introduced in Java 5. The wrappers (including this method) have been there since the original release.

A link to the Javadoc

In that time (1996) we did need the intValue() method and as Oracle guarantees backward backwards compatibility... up to a certain level (it is not always 100% on major releases).

The method has to stay in.

回答2:

In addition to Frank's answer which gives a good historical perspective there is still a need to use the intValue() today in some situations.

Be aware of the following pitfall that shows that you cannot regard an Integer as an int:

 Integer i1 = new Integer(5);
 Integer i2 = new Integer(5);

 //This would be the way if they were int
 System.out.println(i1 == i2); //Returns false

 //This is the way for Integers
 System.out.println(i1.intValue()==i2.intValue()); //Returns true
 System.out.println(i1.equals(i2)); //Returns true

Returns

false
true
true

来源：https://stackoverflow.com/questions/15985928/what-is-the-need-of-an-intvalue-method-if-wrappers-use-unboxing