Java versions are 100% backwards compatible, or close enough. I think you're asking them to make Java forwards compatible..? If so, no, that doesn't make any sense.
Code written for Java 7 runs perfectly on Java 8. Code that uses new Java 8 features doesn't run on Java 7 though, because those features didn't exist then. You upgrade the Java runtime to Java 8 and then it supports the new features. Simple, no?
Code written for Java 7 runs perfectly on Java 8. Code that uses new Java 8 features doesn't run on Java 7 though, because those features didn't exist then. You upgrade the Java runtime to Java 8 and then it supports the new features. Simple, no?