Java basic data types and reference types

These basic data types are not something to come up with.

3 Types of references

Classes Class

Interface interface

Arrays Array

First one: Class

Integer Long Boolean Byte Character Double Float Short These classes

Automatically boxed into an object

The String:string class represents a string, and all string literals (such as "ABC") in a Java program are implemented as instances of this class

String str = "LCY"//STR is a variable of reference type (object can point out method) (object's manager)

Date:date represents a specific moment, accurate to

Second one: interface

List List = new ArrayList (), List of variables for this interface type , Object Manager, owning method

list<e>: list, the user of this interface can precisely control the insertion position of each element in the list. The user can index an integer based on the element

The position in the list) accesses the element and searches for the element in the list.
Add (): Inserts the specified element in the list.
Remove (): Removes the element from the specified position in the list.
Get (int index): Returns the element at the specified position in the list.

Map<k,v>:

Java basic data types and reference types