Java compilation and execution flow - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the first step in the Java compilation process?

The first step is writing the Java source code in a file with a .java extension.

beginner

What does the Java compiler (javac) do?

It converts the Java source code (.java) into bytecode, which is saved in a .class file.

beginner

What is bytecode in Java?

Bytecode is a set of instructions that the Java Virtual Machine (JVM) understands and can execute. It is platform-independent.

beginner

What role does the Java Virtual Machine (JVM) play in execution?

The JVM reads the bytecode from the .class file and executes it on the host machine, making Java programs platform-independent.

beginner

What is the full flow from writing Java code to running a program?

1. Write Java source code in a .java file.
2. Compile the source code using javac to create bytecode .class files.
3. Run the bytecode using the JVM with the java command.

What file extension does Java source code use?

A .java

B .class

C .exe

D .jar

Java source code is saved in files ending with .java.

What does the javac command do?

A Starts the JVM

B Runs Java bytecode

C Packages Java files into a JAR

D Compiles Java source code into bytecode

javac compiles .java files into .class bytecode files.

Which component executes Java bytecode?

A Java Virtual Machine (JVM)

B Java compiler

C Java source code

D Java Development Kit (JDK)

The JVM reads and runs the bytecode on the computer.

Why is Java considered platform-independent?

A Because source code runs directly on all machines

B Because bytecode runs on JVM which is available on many platforms

C Because Java programs are compiled to machine code

D Because Java uses .exe files

Bytecode runs on the JVM, which is available for many operating systems, making Java platform-independent.

What command runs a compiled Java program?

A javac

B javadoc

C java

D jar

The java command runs the Java program by starting the JVM and executing bytecode.

Explain the steps from writing Java code to running it on your computer.

Think about what happens before and after compiling.

Why does Java use bytecode and the JVM instead of compiling directly to machine code?

Consider how Java runs on different computers.