This chapter provided a comprehensive overview of using the Java Development Tools (JDT) to explore, write, and run Java. It described how to create different kinds of Java elements, how to navigate and search them with the different views, and how to write Java code using content assist, code generation, and refactoring. It covered how different kinds of errors are marked and how to fix errors with quick fix. The chapter discussed how to set Javadoc locations and view Javadoc. It looked in some detail at Java projects and their properties, how these properties impact your projects, and how to use different JREs and reference declarations in other projects and JAR files. The chapter also described editing code templates used in code generation and externalizing strings. It explained how to run Java code and how to evaluate Java expressions in a scrapbook page, run Java programs using the Run action, and use launch configurations to run Java programs, including specifying program and JVM parameters.