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.
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.