why do we need to build java code before importing to eclipse for methods autosuggestion

Question

I have a fundamental question, but something which bothers me a lot. We sync code from perforce in my company. and then we are taught to build the code compatible to eclipse. Then we import the code in eclipse as existing project. Then when we hit ctrl-space from an object, we get suggestions of methods.

My question is: Why do we need to build the code for suggestions of methods? . After syncing from perforce, what I have is still an existing java project (right?). So eclipse should be smart enough to be able to index and find out from source code, the methods, when I hit ctrl-space on an object?.

Why do I need to build? What purpose the build serves?

Answer 1

The code does not have to be built, but to be able to import a directory as project via File > Import...: General > Existing Projects into Workspace into Eclipse, at least the file .project must exist.

There are several ways to import, for example, a Maven project:

• Execute mvn eclipse:eclipse on the command line and in Eclipse do File > Import...: General > Existing Projects into Workspace
• File > Import...: Maven > Existing Maven Projects without a command line call uses by default the in Eclipse embedded Maven
• File > Open Projects from File System... (or in Git Repositories view right-click + Import Projects...) detects not only Maven projects but also plain Java projects and automatically configures them accordingly.

In all three ways the following files are created, which are required in Eclipse for the Java content assist (Ctrl+Space) to work:

• .project - says whether it is e. g. a Java, a PHP or a C/C++ project (to be more precise, the project name, builders and natures are specified here, e. g. the project folder icon of a Java Maven project will be decorated with a M and a J based on the Java and Maven project natures)
• .classpath - tells Eclipse where the source and output folders are and which JARs should be added to the classpath (in Maven projects, the JARs are not listed, but it refers to the Maven dependencies which are computed from the pom.xml file)
• .settings/org.eclipse.jdt.core.prefs - contains Java compiler and optional formatter settings (e. g. which Java version; which problems should be ignored or shown as infos, as warnings or as errors, etc.)

With Eclipse Oomph you can automate even more: you select a project and based on a project-specific configuration, for example, a Git repository is automatically cloned and plug-ins necessary to edit the project are automatically installed and configured.