Command line execution in Java - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the command to compile a Java program named HelloWorld.java?

Use javac HelloWorld.java to compile the Java source file into bytecode.

beginner

How do you run a compiled Java program named HelloWorld from the command line?

Use <code>java HelloWorld</code> to run the compiled Java class file.

beginner

What does the java command expect as input after the command itself?

It expects the name of the class containing the <code>main</code> method to start execution.

intermediate

How can you pass arguments to a Java program via the command line?

Add the arguments after the class name in the <code>java</code> command, e.g., <code>java HelloWorld arg1 arg2</code>. These are accessible in the program via the <code>String[] args</code> parameter of <code>main</code>.

beginner

What is the difference between javac and java commands?

<code>javac</code> compiles Java source code into bytecode (.class files). <code>java</code> runs the compiled bytecode on the Java Virtual Machine.

Which command compiles a Java source file named App.java?

A compile App.java

B java App.java

C run App.java

D javac App.java

The javac command compiles Java source files.

How do you execute a compiled Java class named App?

A java App

B javac App

C run App

D execute App.java

Use java App to run the compiled class.

Where do command line arguments appear in a Java program?

A In the <code>Scanner</code> class automatically

B In the <code>System.out</code> stream

C In the <code>String[] args</code> parameter of <code>main</code>

D In the <code>java.util</code> package

Arguments passed on the command line are received in main(String[] args).

What file extension does the Java compiler produce?

A .class

B .java

C .exe

D .jar

The compiler produces bytecode files with the .class extension.

If you run java HelloWorld but get an error, what might be a common cause?

A You forgot to write <code>javac</code> before <code>java</code>

B The <code>HelloWorld.class</code> file is missing or not in the current directory

C You need to add <code>.java</code> extension when running

D Java programs cannot be run from the command line

The java command needs the compiled .class file in the current directory or classpath.

Explain the steps to compile and run a Java program from the command line.

Think about what commands you type and in what order.

Describe how command line arguments are passed to and accessed in a Java program.

Focus on the main method signature and command line syntax.