Invoking jdk 7 compiled class from jdk6

Question

I hava class compiled using jdk7 and I am trying to invoke using JDK6 and the jars in classpath are compiled using jdk 6

jdk6/bin/java com.test.myclass -classpath abc.jar xyz.jar pqr.jar MNO.jar

my class com.test.myclass is present in MNO.jar and abc.jar xyz.jar pqr.jar are compiled with jdk6

with jdk7 it works

jdk7/bin/java com.test.myclass -classpath abc.jar xyz.jar pqr.jar MNO.jar

This also fails.Any input to solve this problem.?

Exception in thread "Main Thread" java.lang.UnsupportedClassVersionError: com/test/MyClass: unsupported classversion 51.0
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
    at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
Could not find the main class: com.test.MyClass.  Program will exit.
256

Thanks

Answer 1

When you compile the sources, give the parameter -target 1.6 . That way 1.6 compliant bytecode will be generated (ie class files will indicate that they need 1.6 or higher to run).

Answer 2

As the last resort you can change the class version at .class file from 33 to 32 (7-th byte from the file beginning) with a hex editor. If the class does not use any Java 7 new feature it will work OK.

Answer 3

如果您在类中使用了任何特定于jdk 7的代码，则它将无法正常运行，否则它将正常运行。