java.lang.UnsupportedClassVersionError: Bad version number in .class file? -

i getting error when include opensource library had compile source. now, suggestions on web indicate code compiled in 1 version , executed in version (new on old). however, have 1 version of jre on system. if run commands:

$ javac -version javac 1.5.0_18  $ java -version java version "1.5.0_18" java(tm) 2 runtime environment, standard edition (build 1.5.0_18-b02) java hotspot(tm) server vm (build 1.5.0_18-b02, mixed mode) 

and check in eclipse properties of java library, 1.5.0_18

therefore, have conclude else, internal class itself, throwing exception?? possible?

i've learned error messages right. when couldn't possibly (in mind) error being reported says, go hunting problem in area...only find out hours later original error message indeed right.

since you're using eclipse, think thilo has right reason getting message because 1 of projects compiling 1.6 classes. doesn't matter if have 1.5 jre on system, because eclipse has own compiler (not javac), , needs 1.5 jre compile 1.6 classes. may weird, , setting needs unchecked allow this, managed it.

for project in question, check project properties (usually alt+enter), java compiler section. here's image of project configured compile 1.6, 1.5 jre.