How to Resolve 'Could Not Find or Load Main Class' Error in Java

What causes the 'Could not find or load main class' error in Java and how can it be fixed?

java -cp /path/to/classes com.example.Main

'Could not find or load main class' is a common error in Java, usually indicating a problem with the classpath or the class definition. This error occurs when the Java Virtual Machine (JVM) cannot locate the specified main class needed to execute your program.

// Example command to run a Java class with the correct classpath:
java -cp /path/to/classes com.example.Main  // Replace with your actual path and class.

Causes

• Class not found in the specified classpath.
• Incorrect package name or class name in the command.
• Compilation errors preventing the class from being generated.
• The class file is missing or not in the expected directory.

Solutions

• Ensure the classpath is set correctly using the '-cp' or '-classpath' option.
• Check that you are using the correct package and class name in your command.
• Compile your Java files properly to make sure the class file exists.
• Confirm that the class files are located in the correct directory.

Mistake: Forgetting to compile the Java file before running it.

Solution: Always compile your Java files with 'javac FirstClass.java' before running with 'java FirstClass'.

Mistake: Misplaced or incorrect spelling of the class or package name.

Solution: Always check for typos in the class and package names.

Mistake: Not updating the classpath after moving files.

Solution: Always revisit the classpath setting if you move your .class files.