It uses the Java interpreter to interpret and execute the bytecode.

Create the source code with a text editor, open a command prompt, use the "cd" command to move to the location of the text editor folder, compile the text editor file with the "Javac" command, and then use the "Java" command. There is a method of executing a class file.

However, this method is so inefficient that most Java applications are created and executed in an integrated development environment such as Eclipse or IntelliJ IDEA. The integrated development environment can not only create, edit, and execute source code, but also perform automatic error checking, code input correction, and function expansion with plug-ins.

Source code creation

A Java application consists of one or more classes and starts with the main method. Classes and methods will be explained later, so please think about it.

The format is as follows.

class ClassName{
        public static void main(String[] args){
                /*
main method
                */
        }
}

Standard output

The output on the result screen such as the command prompt or console view is called standard output.

To output the value as standard output from Java application, use System.out.print () method or System.out.println method. In both cases, specify the value you want to print in (), but the System.out.println () method will start a new line after printing. Basically, Java puts a; (semicolon) at the end of a sentence. Enclose it in "" (double quotation marks) when handling a character string, and use + to concatenate a character string and a numerical value. The following is an example.

 System.out.print(12333);  //12333
 System.out.println("Hello.");  //New line and outputs the Hello
 System.out.println(3+"Chome"); //3とChomeを連結した3Chomeを出力して改行

Precautions when entering source code There are a few things to keep in mind when entering the source code.

・ (), {}, [], Space is half-width

・ Alphabet is case sensitive

・ Alphabets, symbols and numbers are half-width

-Indicate appropriate indentation and comments in an easy-to-understand manner to improve readability.

class ClassName{
        public static void main(String[] args){
               System.out.print(333);
        }
}

//Single line comment

/*Multi-line comment*/

Comment usage example

//I want to eat ramen
/*sleepy

hot

Cold*/

Summary

A programming language is a language for writing source code for creating programs.

Java is a technology that has three aspects: programming language, execution environment, and development environment.

There are three types of Java, Java SE JavaEE Java ME, and Java SE must be introduced.

When developing in Java, it is recommended to develop in an integrated development environment

Java application consists of one or more classes and starts from main method

Source code arranges comments and indents to improve readability

Since this is the first time, I've only explained the terms, but it's okay if you can get a rough idea of the program and Java.

Next time, I will mainly explain identifiers, variables, data types, and operators.