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## Eclipse Build Project: A Comprehensive Guide In the Eclipse IDE, building a project is the process of compiling source code (such as `.java` files) into executable artifacts (such as `.class` files). Eclipse manages this process using **Builders**. This tutorial covers how to configure project builders, manage automatic compilation, and perform manual builds in Eclipse. --- ## Project Builders in Eclipse An Eclipse project can be associated with multiple builders. For a standard Java project, the default builder is the **Java Builder**. However, you can also configure other builders, such as an Ant Builder, Maven Builder, or custom scripts, to run during the build process. ### Viewing and Configuring Project Builders To inspect or modify the builders associated with your project: 1. Right-click on your project in the **Package Explorer** or **Project Explorer** view and select **Properties** (or press `Alt + Enter`). 2. In the left-hand tree menu of the Properties dialog, select **Builders**. !(https://www.runoob.com/wp-content/uploads/2014/12/build_project_builders.jpg) * **Java Builder:** This is the default compiler responsible for compiling Java source files into `.class` bytecode files. * **Adding New Builders:** By clicking the **New...** button on the right, you can associate other build tools (such as an **Ant Builder**, Program, or Launch Configuration) with your Java project. !(https://www.runoob.com/wp-content/uploads/2014/12/ant.jpg) --- ## Automatic vs. Manual Compilation Eclipse provides two primary workflows for compiling your code: **Build Automatically** and **Manual Build**. ### 1. Build Automatically (Incremental Build) By default, Eclipse is configured to compile your code automatically. * **How it works:** Every time you save a modified Java file (`Ctrl + S`), the Java Builder automatically compiles the changes in the background and generates the corresponding `.class` files. * **How to toggle it:** You can enable or disable this feature by navigating to the top menu and checking or unchecking **Project** -> **Build Automatically**. !(https://www.runoob.com/wp-content/uploads/2014/12/build_project_menu.jpg) ### 2. Manual Build If you disable **Build Automatically**, you must compile your project manually. * **Build Project:** Compiles only the files that have changed since the last build. To trigger this, go to **Project** -> **Build Project**. * **Clean...:** Cleans the project by deleting all existing compiled `.class` files and build artifacts, then triggers a fresh rebuild of the entire project. This is highly useful for resolving unexpected compilation state issues. > **Note:** If **Build Automatically** is checked, the **Build Project** option in the menu will be greyed out (disabled) because Eclipse is already handling compilation on the fly. --- ## Summary of Build Actions | Action | Menu Path | Description | | :--- | :--- | :--- | | **Build Automatically** | `Project -> Build Automatically` | Toggles background compilation on file save. | | **Build Project** | `Project -> Build Project` | Manually compiles modified files (only available when "Build Automatically" is disabled). | | **Build All** | `Project -> Build All` (`Ctrl + B`) | Manually compiles all modified projects in the workspace. | | **Clean** | `Project -> Clean...` | Discards all build problems and compiled states, rebuilding the project from scratch. |