There are several online Java compilers and IDEs available that can be useful for quick testing and experimentation with Java code. Here are some of the popular online Java compilers:

1. Repl.it: Repl.it is an online coding platform that supports various programming languages, including Java. It provides an interactive coding environment where you can write, compile, and run Java code in your browser. It also offers collaboration features and allows you to save your code projects.

2. JDoodle: JDoodle is an online compiler that supports Java and several other programming languages. It offers a simple and user-friendly interface for coding, compiling, and running Java programs. JDoodle provides both free and paid plans with additional features.

3. OnlineGDB: OnlineGDB is an online IDE that supports multiple programming languages, including Java. It offers a code editor, compiler, and debugger, making it suitable for more complex Java coding tasks. It also provides a community platform for sharing code snippets and collaborating with others.

4. CompileJava.net: CompileJava.net is a straightforward online Java compiler that allows you to write, compile, and run Java code within your web browser. It’s a minimalistic tool for quick Java code testing.

5. Codiva.io: Codiva is an online Java IDE that focuses on simplicity and speed. It offers real-time compilation and error checking as you type, making it a convenient choice for learning and experimenting with Java.

6. IDEOne: IDEOne is an online compiler and debugger that supports a wide range of programming languages, including Java. It provides a simple interface for coding and running Java programs online.