Interview answers
The difference between Int and Integer
1. From the perspective of both being member variables, the initial value of Integer is null and the initial value of int is 0;
2. From the perspective of storage location, Integer as an object is stored in the heap memory, and the int type is directly stored in the stack memory;
3.Integer is an object type, which encapsulates many methods and properties, making it more flexible for us to use.
Why design encapsulation classes?
Java itself is an object-oriented language, and all operations are based on objects, so encapsulation classes must be designed.
Deep understanding
Both Int and Integer are data types that represent integers, but there are some differences between them.
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Int is the basic data type, and Integer is the encapsulation class. Primitive data types are the most basic data types in the Java language. They are predefined and do not require instantiation. Encapsulation classes are encapsulations of basic data types. They are classes and need to be instantiated before they can be used.
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Int can only represent 32-bit integers, while Integer can represent integers of any size. The value range of Int is -2^31 ~ 2^31-1, and the value range of Integer is -2^31 ~ 2^31-1.
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Int operates faster than Integer because Int is a basic data type and does not require object creation and destruction.
Why design encapsulation classes?
The encapsulation class is designed to solve the problem that basic data types cannot meet the needs of object-oriented programming. In object-oriented programming, we need to encapsulate data and encapsulate data and methods of operating data together to form an object. Basic data types cannot achieve this kind of encapsulation because they have no methods and properties.
for example:
int a = 10; // 基本数据类型
Integer b = new Integer(10); // 封装类
a++; // 基本数据类型可以直接进行操作
b++; // 封装类需要调用方法进行操作
System.out.println(a); // 输出 11
System.out.println(b); // 输出 11In the above example, we can see that basic data types can be operated directly, while encapsulated classes need to call methods to operate. This is because the encapsulated class is a class and needs to be instantiated before it can be used, while the basic data type does not need to be instantiated.