java - Setting JDK in Eclipse

Question

I have two JDKs, for Java 6 and 7.

I want to build my project using both. Initially we only built against 1.6. I see in my project setting I can select 1.5, 1.6 1.7 as the compiler level.

How are these options added to the IDE? I never installed Java 1.5. Suppose I wanted Java 1.4. How would I get this to appear in the list? I have added two different JREs in my IDE preferences, but these are not what appears in the dropdown.

Answer 1

You manage the list of available compilers in the Window -> Preferences -> Java -> Installed JRE's tab.

In the project build path configuration dialog, under the libraries tab, you can delete the entry for JRE System Library, click on Add Library and choose the installed JRE to compile with. Some compilers can be configured to compile at a back-level compiler version. I think that's why you're seeing the addition version options.