How to Compile a Java Program Using an SDK or Online Compiler

Last Updated: December 23, 2023

This article was co-authored by Jessica Andzouana and by wikiHow staff writer, Nicole Levine, MFA. Jessica Andzouana is a Software Engineer based in the San Francisco Bay Area. With over five years of professional experience in front-end development, digital art, and design, she is passionate about emerging technologies such as blockchain and AI. Her background as both a programmer and artist, paired with a highly design-conscious mindset, provides her a fresh perspective and unique skill set to produce creative solutions in her field. She works at Alcacruz as a Software Engineer, and received a dual BS/BA degree from Santa Clara in Computer Science and Studio Art.

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Things You Should Know

1. Step 1 Open the command prompt.
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   Open the command prompt. You can use the Java Software Development Kit (Java SDK) from the command prompt on Windows, macOS, or Linux.^[1] If you don't have the Java SDK installed, see How to Install the Java Software Development Kit. Here's how to get to the command prompt on each system:

   • Windows: Right-click the Start menu and select Command Prompt. If you don't see this option, type cmd into the Windows Search bar and click Command Prompt in the search results.
   • macOS: Click the magnifying glass at the top-right corner of the screen to open Spotlight, type terminal, and then click Terminal in the search results.
   • Linux: Press Ctrl+Alt+T.
2. Step 2 Use the cd command to access the directory with your Java code.
   2
   Use the cd command to access the directory with your Java code. The source code is the file that ends with the .java file extension.^[2]
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3. Step 3 Type javac sourcecode.java and press ↵ Enter or ⏎ Return.
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   Type javac sourcecode.java and press ↵ Enter or ⏎ Return. Replace sourcecode.java with the name of your source file.^{[3] [4]} This compiles your source code into an executable file, which ends with the .class extension.

   • To see the name of the new file in the current directory, run the dir (Windows) or ls -a (Mac/Linux) command.
   • If you see an error when trying to
4. Step 4 Type java programname and press ↵ Enter or ⏎ Return.
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   Type java programname and press ↵ Enter or ⏎ Return. Replace programname with the name of your program. This runs the program at the command line.
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1. Step 1 Navigate to https://www.codiva.io...
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   Navigate to https://www.codiva.io in a web browser. Codiva is an online Java compiler that's great for people who can't install a compiler locally—it can even be used on a phone or tablet.

   • There are a variety of online compilers out there if Codiva doesn't work for your needs. Some other popular options are Jdoodle, and OnlineGDB.
2. Step 2 Sign in or create an account.
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   Sign in or create an account. If you're new to Codiva, click Create Account at the top-right corner to sign up.
3. Step 3 Enter a project name and click Create.
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   Enter a project name and click Create. This creates a new project, which is like a container for your source files.^[5]
4. Step 4 Create a Java source file and click Create.
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   Create a Java source file and click Create. Java source files must end with the .java file extension. The new file will appear in project's tree, which appears in the right panel.

   • For example, if you're creating a Java program called HelloWorld, name the source file HelloWorld.java.
5. Step 5 Write or paste your code into the editor.
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   Write or paste your code into the editor. The code will compile in the background as you type. Additionally, it will display any code errors as they occur.
6. Step 6 Click Run to run the program.
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   Click Run to run the program. Since the code compiles automatically, clicking Run will just launch your app in its current state.
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