Tuning the Performance of JDT
In the section "Customizing Eclipse" in Chapter 2, we discussed a number of factors that affect performance of Eclipse, including startup time and memory usage. These included the number of installed tools; how many views, editors, and projects are open; and the number of resources they contained. There are several other factors that can also affect the performance of the JDT. These relate to the amount of real-time processing JDT does to analyze and build code you're editing. If your performance degrades, there are a number of things you can do to improve performance. Some of these things apply across all projects, while others are specific to the JDT. Obviously, each also involves tradeoffs of performance for capability.
Reduce the amount of Java code in your workspace. Do this by partitioning code into multiple workspaces and/or closing projects you're not currently working on.
Under Workbench preferences, deselect Perform build automatically on resource modification. If you do this, you will need to perform builds manually by selecting Project > Rebuild Project from the menu.
Under Java preferences, for Update Java views, select On save only.
Under Java > Editor preferences, on the Code Assist page, deselect Enable auto activation. On the Problem Identification page, deselect any of the three options.