Second, the basic data types

1, the basic data types

1. Numeric
   1. Integer types: byte, short, int, long
   2. Floating-point types: float, double
2. Character: char
3. Boolean: boolean

2, variables and constants

1. Variable: When we define variables, is to tell the compiler that we need much space to store this value, and this value will become, so called variable.

Data area (DATA) ----> program area (Program) ----> System area (OS)

• During program execution, values ​​are placed in the data area, the program is read into memory in the program area.

1. Member variables: variables defined in the body called a class member variables.
   1. Examples of variables: x as an example
   2. Static variables: y is a static variable, can be preceded by static,
      the difference is that static variables can be accessed in the whole application - name of the class variable name. .

public class First{
    int x = 45;
    static char y = "a";
    public static void main(String[] args){

    }
}

3, local variables

1. Class variables defined in the body of the method is called local variables.
   [Comment]: when calling the method, create memory memory space for local variables, after completion of the method of execution, release the corresponding memory space to achieve garbage collection.