CSDN training day 3 (JAVA practice)



Current tasks

1, Download of java development tools and configuration of its environment

2, Java knowledge involved

3, Code conversion is mentioned

4, Appendix (some quick input of IDEA)

5, Summary


  • How do programs help humans improve productivity? What does the program world consist of? If you want to be like a duck to water in JAVA, you must first understand the basic syntax of JAVA programs.
  • I have studied Java for one year. This paper will write an article on how to realize salary conversion in java with the most basic syntax and easy to understand way.
  • This article summarizes my problems in learning and downloading, hoping to help novice Xiaobai!

Current tasks

Realize salary conversion in Java

The user inputs the monthly salary and calculates the daily salary (22 working days per month) and annual salary (13 salary per year)

1, Download of java development tools and configuration of its environment

1.jdk configuration

Note: if you install the eclipse development tool, you must configure the JDK first, otherwise it will not open

about JDK I have packaged the download and its configuration as follows:
Link: https://pan.baidu.com/s/1tOuN1NJUK83dzviuI9pfzA 
Extraction code: myql

2. Download of java development tools

        The development tools I have used include eclipse and IDEA. Compared with IDEA, the function of IDEA is better and more perfect, and many plug-ins can be installed. Now the company basically uses IDEA for development.

        Therefore, following the trend, it is recommended to download IDEA (sorry: due to limited time, please refer to the attached link)

1. about eclipse The installation package has been sorted as follows: ​ 

Link: https://pan.baidu.com/s/1hKgt1XVMGQ9OGz6R31trJA extraction code: s3ch

Because Baidu network disk takes too much trouble

jdk installation and environment configuration and eclips e installation and configuration tutorial are attached: eclipse installation tutorial - the most detailed installation of java_ A Scorpio procedural ape - CSDN blog_ eclipse installation tutorial

2.IDEA Download of
Link: https://pan.baidu.com/s/1WFa5d5zdAh3uI-jFmLoAcQ 
Extraction code: ojkq

Attach IDEA official website: Download IntelliJ IDEA: The Capable & Ergonomic Java IDE by JetBrains

3.about IDEA Download FAQ summary

2, Java knowledge involved

1. Declaration and use of variables in Java

  • In a program, each variable must be declared before being used.

  • Variables can be defined at any time in Java language programs, which does not need to be concentrated before executing statements.

  • In addition to types, variables in the Java language also have modifiers to limit their use. Modifiers include public, protected, private and static. The general form of variable declaration is as follows: < modifier list > < variable type > < variable name list >; For example: static int b=1; The variable name must be a legal identifier. Variables can be initialized when declared. Mu lt iple variables of the same type are declared at a time, separated by commas.

  • A variable in a method must be assigned a value before use.

2. Usage of Scanner class in Java

  • The data entered by the keyboard, whether text or numbers, is regarded as a string in Java. Therefore, if you want to enter numbers by the keyboard, it must be converted again

  • In order to simplify the input operation, a new class named Scanner for input operation has been added to the java.util class library since Java SE 5. You can use this class to input an object

  • Use the Scanner class to input from the console and create its object to read the input from System.in: Scanner input = new Scanner(System.in); (the Scanner class is in the package java.util and needs to be imported in the first line) the object can call the nextDouble() method to obtain a double value, double d = input.nextDouble();

    For more details, see: https://www.runoob.com/java/java-scanner-class.html

3.Java formatted output

  • System.out.printf(): java SE5 has introduced the C language printf() style formatted output function.

  • System.out.format(): the format() method introduced by Java SE5 imitates the printf() method of C and can be used for PrintStream or PrintWriter objects, including System.out objects. The usage is basically similar to System.out.printf().

  • Fomatter class: all formatting functions in Java are handled by the java.util.Formatter class. When you create a Formatter object, you need to pass some information to its constructor to tell it where the final result will be output.

  • String.format(): String.format() is a static method that receives the same parameters as Formatter.format(). Its return value is a string object, which is suitable for one-time output.

    For more details, see: https://blog.csdn.net/qq_44111805/article/details/112850550

4. Main functions and usage of Java decimalformat

  • Keep a few decimal places and comply with the principle of rounding

  • Provides several ways to retain decimal places

    1. use java.math.BigDecimal
    2. use java.text.DecimalFormat 
    3. use java.text.NumberFormat 
    4. use java.util.Formatter 
    5. use String.format 
For more details, see:


3, Code conversion is mentioned

The idea is as follows:

  1. Print out monthly salary first;

  2. Enter monthly salary on the keyboard (realized by Scanner method);

  3. Define monthly salary (the number you type) as mouthSalary;

  4. Define annual salary and daily salary and perform salary conversion: daily salary = monthly salary / 22; Annual salary = monthly salary * 13;

  5. Print the output result (through String.format, two decimal places are reserved).

Specific code:

import java.util.Scanner;       //  Introduce Scanner class
public class Salary conversion {
    public static void main(String[] args) {
        //  Enter title
        System.out.println("***Salary conversion tool v1.0***");
        //  Enter monthly salary
        System.out.print("Please enter monthly salary (RMB): ");
        Scanner sc = new Scanner(System.in);        //  Receive data from keyboard
        //  Salary conversion: daily salary = monthly salary / 22; Annual salary = monthly salary * 13
        double mouthSalary=sc.nextDouble();         //  Define monthly salary (the number you type) as moushsalary
        double daySalary = mouthSalary/22;
        double yearSalary = mouthSalary*13;
        //  Print the output result (two decimal places are reserved through String.format)
        System.out.println(String.format("Your daily salary: ¥%,.2f", daySalary));   //  1
        System.out.print(String.format("Your annual salary: ¥%,.2f", yearSalary));    //  2
        /*Replace daySalary at 1 with mouthSalary/22
              2 Replace yearSalary at with mouthSalary*13
          Code optimization
        eg: System.out.println(String.format("Your daily salary: ¥%,. 2F ", mouthsalary / 22);   //   one
            System.out.print(String.format("Your annual salary: ¥%,. 2F ", mouthsalary * 13);

design sketch:


There are many codes to realize this task. Here is the most basic method!

4, Appendix (some quick input of IDEA)

1. Fast writing of main method

input psvm You can import   public static void main(String[] args) {}
input sout You can import   System.out.println();

2. Most commonly used shortcut keys

Alt+Enter Universal shortcut key for introducing error packages
Ctrl+ Mouse left Quick transfer definition
More short prompt completion statements  Ctrl + J  -------------Shortcut key view

3. See the following blog for other shortcut keys


5, Summary

Combined with myself, this paper summarizes the problems that novice Xiaobai may encounter. Thank you for your love and support, as well as the author of the blog I quoted!!!

Tags: Java Eclipse intellij-idea

Posted on Thu, 28 Oct 2021 16:24:31 -0400 by raymedia