Essential Java Terminal Commands — A Practical Cheat Sheet

If you're starting out with Java or simply prefer working from the terminal (like I sometimes do), or simply wish to play around with terminal, knowing the right commands can save you a lot of frustration. So, here's a practical guide to the most common javac, java, and jar terminal commands.

---

🛠️ 1. Compile a Java File

javac MyClass.java

This compiles MyClass.java into MyClass.class. Think of it as converting your code into something the JVM can understand.

---

▶️ 2. Run a Compiled Class

java MyClass

Runs the MyClass.class file. Do not add .class when running it.

---

📁 3. Compile with Output Directory

javac -d out MyClass.java

This puts the compiled .class file inside an out folder.

Useful when you want to keep things clean — especially for larger projects.

---

📂 4. Compile Multiple Files

javac *.java

Compiles all .java files in the current folder. Simple and effective.

---

📦 5. Compile with Classpath (External Libraries)

javac -cp libs/library.jar MyClass.java

Tells Java to include external .jar files when compiling.

Alternative:

javac -classpath libs/library.jar MyClass.java

Same thing, just longer syntax.

---

🔁 6. Run with Classpath

java -cp .:libs/library.jar MyClass

Use : on Mac/Linux, ; on Windows:

java -cp .;libs/library.jar MyClass

---

📦 7. Create a Simple JAR File

jar cfv MyApp.jar MyClass.class

• c → create

• f → name of jar file

• v → show what’s being added

---

🚀 8. Create an Executable JAR (With Main-Class)

jar cfe MyApp.jar MyClass MyClass.class

• e → set entry point (Main-Class)

• This creates a JAR you can run directly.

---

▶️ 9. Run a JAR File

java -jar MyApp.jar

Runs the JAR if it has a proper Main-Class in its manifest.

---

🔍 10. View JAR Contents

jar tf MyApp.jar

Lists the contents of the JAR. Great for double-checking what went in.

---

⚡ Bonus Commands

🔄 Compile + Run in One Line

javac MyClass.java && java MyClass

Convenient for testing small programs quickly.

📚 Compile All Java Files Recursively

javac -d out $(find . -name "*.java")

Compiles all .java files in the current folder and subfolders.

🧹 Delete All .class Files

find . -name "*.class" -delete

Use this when you want a clean slate (especially before a fresh build).