How to Execute the Java Program

Whether building your first CLI app or integrating Java into larger projects, here’s your go-to guide for writing, compiling, and running Java programs—optimized for speed and clarity.

📄 1. Write Your Java Code

🔹 Naming Conventions Matter

Save the file with a .java extension (e.g., MyProgram.java).

The public class name must match the filename exactly (case-sensitive).

✨ Sample Code

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

💡 Tip: Always include public static void main(String[] args) for standalone Java apps.

☕ 2. Install the JDK (Java Development Kit)

🔍 Check If It’s Already Installed

java -version     # JRE
javac -version    # Compiler (JDK)

📦 Recommended Installation Methods

Linux/macOS (fastest way): sdk install java # via SDKMAN brew install openjdk # macOS
Manual Install:
- Adoptium OpenJDK
- Oracle JDK

🛠️ 3. Compile and Run Java from the Command Line

✅ Compile

cd /path/to/code
javac MyProgram.java   # Produces MyProgram.class

🔹 Want to organize compiled files?

javac -d bin MyProgram.java

🚀 Run

java MyProgram

Expected Output:

Hello, World!

🧩 4. Fix Common Errors Fast

Error	Likely Cause / Fix
`javac: command not found`	JDK not installed or `$PATH` misconfigured
`ClassNotFoundException`	Wrong class name or `.class` file missing
`';' expected`	Syntax error—check your code

✅ Environment Setup Checklist

export JAVA_HOME=/path/to/jdk
export PATH=$JAVA_HOME/bin:$PATH

⚡ 5. Boost Your Java Workflow

💻 Use IDEs to Save Time

These IDEs handle compilation, execution, and even debugging out of the box.

🧱 Use Build Tools for Project Management

Maven and Gradle simplify dependency management and build automation.

📦 Handle External JARs

javac -cp .:lib/* MyProgram.java
java -cp .:lib/* MyProgram

🔧 6. Advanced Tips for Clean Code and Projects

📁 Using Packages

If your class is part of a package:

package com.example;

Save it in com/example/MyProgram.java and run:

javac com/example/MyProgram.java
java com.example.MyProgram

⭐ Wildcard Compilation

javac *.java   # Compiles all Java files in the directory

✅ Conclusion

From setting up your environment to handling large Java projects, mastering the Java CLI flow gives you better control, faster debugging, and more confidence in your code.

Mastering Java’s contains() Method

base64.decode java- complete guide