Detailed explanation of the difference between int and Integer in Java

1. Data types in Java are divided into basic data types and complex data types

int is the former, and integer is the latter (that is, a class).

2. During initialization

int i = 1;

 Integer i = new Integer(1);   // (要把integer 当做一个类看)

int is the basic data type (a trace left by the process, but a useful supplement to Java)

Integer is a class, an extension of int, and defines many conversion methods

Similar ones include: float Float, double Double, string String, etc.

For example: when you need to put things into ArrayList or HashMap, built-in types such as int and double cannot be put in, because the containers are all for objects, so these built-in types are needed. Create a covering class for the type.

Every built-in type in Java has a corresponding covering class.

The relationship between int and Integer in Java is relatively subtle. The relationship is as follows:

1. Int is the basic data type;

2. Integer is the encapsulation class of int;

3. Both int and Integer can represent a certain value. ;

4. Int and Integer cannot be used interchangeably because they are two different data types;

Example:

 ArrayList al=new ArrayList();
 int n=40;
 Integer nI=new Integer(n);
 al.add(n);//不可以
 al.add(nI);//可以

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