JShell is an interactive tool introduced in Java 9 that provides a Read-Eval-Print Loop (REPL) for Java. It allows developers to quickly write, test, and explore Java code snippets without the need to create a full class or project structure.**** JShell is aimed at improving developer productivity, learning, and experimentation with Java APIs and features.
Key Features
- Immediate Feedback: Evaluate Java expressions and see results instantly.
- No Boilerplate: Execute statements without defining classes or a
mainmethod. - Exploratory Programming: Quickly test logic, APIs, libraries, or new Java features.
- Command Set: Special commands (starting with
/) for saving sessions, listing variables, viewing history, etc. - Import Support: Easily import Java packages for use in snippets.
Useful Commands
| Command | Description |
|---|---|
/help | List available JShell commands |
/vars | List declared variables |
/methods | List declared methods |
/list | Show command history |
/save <file> | Save current session to a file |
/open <file> | Load and run code from a file |
/reset | Clear all definitions |
/exit | Exit JShell |
Limitations
- Designed for interactive use, not full application development.
- Session state is temporary unless explicitly saved.
- Not all complex project setups (like dependency management, advanced classpath setups) are easily handled inside JShell.