JShell REPL & Launching Single-File Source Code (Java 11+)

1Concept

Java 9 introduced JShell (Interactive REPL) for rapid prototyping without writing full boilerplate classes. Java 11 introduced single-file execution: `java App.java` runs directly without pre-compiling `javac App.java` to disk.

2Architecture Diagram

Source File (App.java) ---> [ Direct `java App.java` Execution ] ---> Memory Compiled & Run (No .class written to disk)

3Code Example

public class SingleFileLauncher {
    public static void main(String[] args) {
        System.out.println("Direct execution without javac step supported in Java 11+");
        System.out.println("Arguments Passed: " + String.join(", ", args));
    }
}

4Expected Output

Direct execution without javac step supported in Java 11+
Arguments Passed: 

5Key Takeaways

• ✓Use JShell for testing quick APIs, math expressions, and stream pipelines.
• ✓Single-file launcher `java Script.java` compiles to memory and executes instantly.
• ✓Ideal for shell automation scripts and lightweight application prototypes.