Java review-1

You can use cmd command line to run Java in Windows, the running process is as follows:

javac name.java //Compile

java name //Run

Run java name.java directly in Linux

//test_1  HelloWorld
package Day_1;

public class HelloWorld {
    //main方法，是程序执行的起点
    public static void main(String[] args){
        //打印信息
        System.out.print("Hello,World!!!!!!!!!");
        System.out.print("真好！");
    }
}

 

Character type:

Integer: int 1 2 123 94798470 -12331

Floating point number (decimal constant): 2.5 -3.14 0.0

String constant: "something surrounded by double quotes"

Character constant:'constant enclosed in single quotes'

Boolean constant: true false

Empty constant: null ---cannot be printed directly

Note: the double quotation mark can be empty

        Single quotation marks cannot be empty or have multiple characters

 

------------------Keywords:

    1. Completely lowercase letters (such as: public, not, true, flase, int, static...)

    2. There are special colors in the enhanced programming tool

type of data:

Basic data types:

-----Integer byte(1) short(2) int(4) long(8)

----- Floating point type float (4) double (8)

-----Character type char

-----Boolean boolean

Reference data type:

-----String, Array, Class, Interface, Lambda

 

 

(to be continued)