5. What is the difference between int and Integer?

One. Basic usage comparison

int is a basic data type, and the default value is 0 when used as a member variable.

Integer is a wrapper class for int. When used as a member variable, the default value is null.

int can be used directly without instantiation, and Integer can be used after instantiation.

int stores the value directly, while Integer is a reference to the object.

2. Compare size processing (using ==)

Usually compare the same numbers:

1. An int and an Integer:

int a=5;Integer b=5;a==b;//true

Integer objects are automatically unboxed and compared to int data.Return true.

2. Two new Integers: because they are both new objects, they are actually two different objects, not equal.Return false.

Integer a=new Integer(5);Integer b=new integer(5);a==b;//false

3. One new and one not new: In fact, it is still a comparison of objects, and it should be that different objects are not equal.return false;

Integer a=5;Integer b=new Integer(5);a==b;//false

4. Neither are new

The first case: the value is between -128-127, return true

Integer a=5;Integer b=5;a==b;//true

The second case: the value is not between the above ranges, return false

Integer a=300;integer b=300;a==b;//false

Reason: When the value is between -128-127, Integer a=5; it will be translated as Integer i = Integer.valueOf(5).The definition of valueOf of Integer type in the java API is as follows. For numbers between -128 and 127, it will be cached. When Integer a=5, 5 will be cached, and when Integer b=5 is written next time, it will be cached.It will be taken directly from the cache, and there will be no new.