Understanding the subtle yet crucial differences between ‘java’, ‘javaw’, and ‘javaws’ is fundamental for any Java developer. These three commands, though related, serve distinct purposes in executing Java code. Knowing when to use each one can significantly impact how your applications run and interact with the operating system. This article will delve into the functionalities of each command, providing practical examples and scenarios to clarify their usage. We’ll explore how they handle console output, window management, and the deployment of Java Web Start applications, ensuring you have a comprehensive understanding of the Java runtime environment. This knowledge is essential for troubleshooting, optimizing, and effectively deploying Java applications across various platforms.

Java: The Core Execution Command

The ‘java’ command is the cornerstone of Java application execution. It’s the primary tool used to launch Java applications from the command line. When you execute ‘java YourClass’, the Java Virtual Machine (JVM) is invoked, loading the specified class ‘YourClass’ and executing its main method. This command is designed for applications that require console interaction, such as command-line tools, server applications, or any program that outputs text to the console. It’s the standard way to run most Java applications during development and testing.

One of the key characteristics of the ‘java’ command is its direct association with the console. Any output generated by the application, including System.out.println statements and error messages, is displayed in the console window. This makes it ideal for debugging and monitoring applications during development. However, this behavior might not be desirable for graphical user interface (GUI) applications, where the console window can be visually distracting or unnecessary. The ‘java’ command also accepts various command-line options that allow you to configure the JVM, set system properties, and manage the classpath. For example, using the ‘-Xms’ and ‘-Xmx’ options, you can control the initial and maximum heap size allocated to the JVM.

Consider a simple Java program that prints “Hello, World!” to the console. Executing this program with the ‘java’ command will display the output in the console window. This is the expected behavior for console-based applications. However, if you were to run a GUI application using the ‘java’ command, a separate console window would appear alongside the GUI, potentially cluttering the user interface. This is where ‘javaw’ comes into play. The ‘java’ command is best suited for scenarios where console interaction is essential, providing a direct channel for output and error messages. According to Oracle documentation, “The java command launches a Java application. It does this by starting a Java runtime environment, loading a specified class, and invoking that class’s main method.” Oracle Java Documentation

Javaw: Running GUI Applications

The ‘javaw’ command is specifically designed for executing Java applications that have a graphical user interface (GUI). Unlike the ‘java’ command, ‘javaw’ launches the JVM without associating it with a console window. This means that any output generated by the application, such as System.out.println statements, will not be visible. This behavior is ideal for GUI applications, as it prevents an unnecessary console window from appearing and cluttering the user interface. Applications launched with ‘javaw’ run silently in the background, providing a cleaner and more professional user experience.

The primary difference between ‘java’ and ‘javaw’ lies in their handling of the console. While ‘java’ creates and associates with a console window, ‘javaw’ does not. This distinction is crucial for GUI applications, where the presence of a console window is often undesirable. When you double-click a Java application packaged as an executable JAR file, the operating system typically uses ‘javaw’ to launch the application, ensuring that no console window appears. This is the standard behavior for most desktop Java applications. However, it’s important to note that if the application encounters an error and attempts to print an error message to System.err, the message will not be visible when using ‘javaw’. In such cases, developers often resort to logging error messages to a file for debugging purposes.

For example, consider a Java Swing application that displays a simple window with buttons and text fields. Running this application with the ‘javaw’ command will launch the GUI without any console window. This provides a seamless user experience, as the application appears as a standalone desktop application. In contrast, running the same application with the ‘java’ command would result in both the GUI window and a console window being displayed. Therefore, ‘javaw’ is the preferred choice for deploying GUI applications, ensuring a clean and user-friendly interface. As stated in a Stack Overflow discussion, “javaw is the same as java, except that javaw does not have an associated console window.” Stack Overflow Discussion

Java Web Start (javaws): Deploying Rich Internet Applications

Java Web Start (javaws) is a technology that allows you to deploy and launch Java applications over the internet. It enables users to run Java applications directly from a web browser with a single click, without requiring them to manually download and install the application. Java Web Start simplifies the deployment process, making it easier for users to access and use Java applications. The ‘javaws’ command is used to launch Java Web Start applications, typically packaged as JAR files and described by a JNLP (Java Network Launching Protocol) file.

The JNLP file contains metadata about the application, including its name, version, main class, and dependencies. When a user clicks on a JNLP file, the ‘javaws’ command is invoked, which downloads the application from the specified URL and launches it in a secure sandbox environment. This sandbox environment restricts the application’s access to system resources, mitigating security risks. Java Web Start also provides automatic update functionality, ensuring that users always have the latest version of the application. When a new version is available, Java Web Start automatically downloads and installs it, providing a seamless update experience. However, it is important to note that Java Web Start has been deprecated in later versions of Java, and developers are encouraged to migrate to alternative deployment technologies.

A practical example of Java Web Start is deploying a complex data analysis tool. Instead of requiring users to download and install the application, you can simply provide a link to the JNLP file on a web page. When users click the link, the application is launched directly from their browser, providing a convenient and user-friendly experience. Java Web Start also handles dependency management, ensuring that all required libraries are downloaded and installed automatically. This simplifies the deployment process and reduces the risk of compatibility issues. However, due to its deprecation, consider exploring alternatives like web-based technologies or modern application packaging solutions. For a comprehensive overview of Java Web Start, refer to the official Oracle documentation. Oracle Java Web Start Tutorial

Key Differences Summarized

To effectively utilize ‘java’, ‘javaw’, and ‘javaws’, understanding their core functionalities and typical use cases is crucial. Here’s a comparison table that highlights the key differences:

• Java (‘java’): Executes Java applications with console interaction. Displays output and error messages in the console window.
• Javaw (‘javaw’): Executes Java GUI applications without a console window. Ideal for providing a cleaner user experience.
• Java Web Start (‘javaws’): Deploys and launches Java applications over the internet. Simplifies deployment and provides automatic updates.

Choosing the right command depends on the type of application you are running and the desired user experience. For console-based applications, ‘java’ is the appropriate choice. For GUI applications, ‘javaw’ provides a cleaner and more professional appearance. For deploying applications over the internet, Java Web Start (javaws) offers a convenient and user-friendly solution, although its deprecation warrants exploring alternative technologies.

1. ‘java’: Use for command-line tools, server applications, and any program that requires console output.
2. ‘javaw’: Use for GUI applications to prevent a console window from appearing.
3. ‘javaws’: Use for deploying Java applications over the internet (consider alternatives due to deprecation).

Choosing the correct command ensures that your Java applications run smoothly and provide the best possible user experience. For example, if you are developing a server-side application that processes data and logs information to the console, you would use the ‘java’ command to execute it. On the other hand, if you are creating a desktop application with a graphical user interface, you would use the ‘javaw’ command to launch it without a console window. Java Web Start (‘javaws’) was ideal for deploying rich internet applications, simplifying the distribution and update process for end-users. Properly understanding the differences between these commands is essential for every Java developer.

Here’s a featured snippet-optimized paragraph:

The key difference between ‘java’ and ‘javaw’ lies in console handling. ‘Java’ launches applications with a console window, displaying standard output and error messages. Conversely, ‘javaw’ executes applications without a console, making it suitable for GUI applications where console visibility is undesirable. ‘Javaws’ is distinct as it’s designed for deploying and running applications over the web via Java Web Start, a technology that simplifies application distribution and updates, although it is now considered deprecated.

• ‘java’ is associated with the console.
• ‘javaw’ suppresses the console window.
• ‘javaws’ facilitates web-based deployment.

Learn more about Java performance tuningFAQ Section

What happens if I use 'java' for a GUI application?

A console window will appear alongside the GUI, which might be undesirable for the user experience.

Can I see error messages when using 'javaw'?

No, 'javaw' suppresses the console, so error messages printed to System.err will not be visible. Consider logging errors to a file.

Is Java Web Start still recommended?

Java Web Start is deprecated, so it's recommended to explore alternative deployment technologies.

What are the alternatives to Java Web Start?

Alternatives include web-based technologies, containerization (e.g., Docker), and modern application packaging solutions.

Question & Answer :
What is the difference between java, javaw, and javaws?

I have found that on Windows most usage of Java is done using javaw.

See Java tools documentation for:

• java command¹/javaw command²

1. The java tool launches a Java application. It does this by starting a Java runtime environment, loading a specified class, and invoking that class’s main method.
2. The javaw command is identical to java, except that with javaw there is no associated console window. Use javaw when you don’t want a command prompt window to appear.

• javaws command, the "Java Web Start command"

The javaws command launches Java Web Start, which is the reference implementation of the Java Network Launching Protocol (JNLP). Java Web Start launches Java applications/applets hosted on a network.

If a JNLP file is specified, javaws will launch the Java application/applet specified in the JNLP file.

The javaws launcher has a set of options that are supported in the current release. However, the options may be removed in a future release.

See also JDK 9 Release Notes Deprecated APIs, Features, and Options:

Java Deployment Technologies are deprecated and will be removed in a future release
Java Applet and WebStart functionality, including the Applet API, the Java plug-in, the Java Applet Viewer, JNLP and Java Web Start, including the javaws tool, are all deprecated in JDK 9 and will be removed in a future release.