Build classpath

The build classpath is the path which is used to find classes that are referenced by your source code. During compilation, this path is used to search for classes outside of your project. The build classpath is specified for each project. In the project properties, it is referred to as the "Java Build Path."

Java builder
Classpath variable

Adding a JAR file to the build path
Adding a library folder to the build path
Building a Java program
Building automatically
Building manually
Viewing and editing a project's build path
Working with build paths
Creating a new source folder with exclusion filter
Creating a new source folder with specific output folder

Classpath Variables preferences
Java Build Path properties