How to write a java program?
A Java program can be thought of as a collection of objects that work together by calling each other's methods. The following briefly introduces the concepts of classes, objects, methods and instance variables.
Recommended tutorial: "java learning"
Object: An object is an instance of a class, with state and behavior. For example, a dog is an object. Its status includes: color, name, and breed; its behaviors include: wagging its tail, barking, eating, etc.
Class: A class is a template that describes the behavior and status of a type of object.
Method: Method is behavior, and a class can have many methods. Logical operations, data modification, and all actions are completed in methods.
Instance variables: Each object has unique instance variables, and the state of the object is determined by the values of these instance variables.
Method/Step
1. Open Notepad or other text tools and add the above code into it
2. Enter the file name Save as: HelloWorld.java;
3. Open the cmd command window and enter the location of the target file, assuming it is C:\
4. Type javac HelloWorld.java in the command line window and press Press the enter key to compile the code. If there are no errors in the code, the cmd command prompt will go to the next line. (Assuming the environment variables are all set).
5. Type java HelloWorld and press the Enter key to run the program. You will see Hello World in the window
Notes
Case sensitivity: Java is case-sensitive, which means that the identifiers Hello and hello are different.
Class name: For all classes, the first letter of the class name should be capitalized. If the class name consists of several words, the first letter of each word should be capitalized, for example, MyFirstJavaClass . Method names: All method names should start with a lowercase letter. If the method name contains several words, the first letter of each subsequent word is capitalized.
Source file name: The source file name must be the same as the class name. When saving the file, you should use the class name as the filename (remember Java is case-sensitive) and the filename suffix .java. (If the file name and class name are different, a compilation error will occur).
Main method entrance: All Java programs start execution from the public static void main(String []args) method.
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