In terms of use

1, Basic data type : Judge whether the data are equal , use == and != Judge .

2, Reference data type : Judge whether the data are equal , use equals() Method ,== and != It's numerical . and equals() By comparing memory

Address of the .

Add ： The principle of data type selection

If you want to represent an integer, use int, For decimal, use double;

If you want to describe a date time number or represent a file （ Or memory ） It's about size long;

If you want to achieve content delivery or code conversion, use byte;

If we want to realize the control of logic , have access to booleam;

If you want to use Chinese , Use char Avoid miscoding in Chinese ;

If according to the scope of preservation ：byte < int < long < double;

// The basic data type is called as a method parameter

public class Main{

public static void main(String[] args){

// Basic data type

int i = 1;

int j = 1;

double d = 1.2;

// Reference data type

String str = "Hello";

String str1= "Hello";

}

}