I need to compile a project for Java 6 to use with java 6 or 7 (I can't upgrade all of the computers in my life). I've been searching all over and found somewhat helpful stuff, but I'm rather new to java - I don't understand much of how to use the presented alternatives (ant-build, Maven, javac).
My program does not use any API methods that are not available in Java 6, but it does use the API of another external .JAR (it is a basic plugin for an example program)
Is there a simple way to do this with Eclipse's Export function, or do I need to use some other program/method?
If I need to use something other than Eclipse, how would I best go about doing it for a multi-class, multi-package file dependent on another external .jar's API?
Right-click on your project in eclipse and open the project properties.
Then navigate to Java compiler and set the compliance level to 1.6.
That should do it.
In Eclipse Juno SR1: right click your project -> Properties -> Java Compiler -> Compiler compliance level.
Set that to 1.6 and you're done. You might need to enable project specific settings and disable compliance with execution environment - 2 checkboxes in the same window.
来源：https://stackoverflow.com/questions/14705324/compiling-java-7-for-java-6-with-eclipse