Java error: Reasons and solutions for main class not found or unable to be loaded

1. Problem location

When compiling (javac) and executing (java) java program, this type of error occurs: cannot be found or cannot load the main class: (Recommended: java video tutorial)

1. First, rule out whether the problem is caused by improper configuration of environment variables. Just make sure that the command line interface can recognize javac/ java command, it means that there is no problem with the environment variable configuration.

2. This problem often occurs because the java source file contains a package name, such as the file C:\code\Hello.java:

package com.example;

public class Hello{
    public static void main(String[]args){
        System.out.println("Hello");
    }
}

It seems that there is no problem, Execution:

C:\code>javac Hello.java
C:\code>java Hello
错误: 找不到或无法加载主类 Hello

2. Solution

Delete the package name from the source file (not recommended);

Create it under code with the same name as the package The file path structure (C:\code\com\example\Hello.java)

编译:C:\code>javac com/example/Hello.java
运行:C:\code>java com.example.Hello

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