Do we need to compile JAR for JDK upgrade?

Question

For our java project, we use several JAR libraries. Some of the source code for the JAR libraries have been lost.

We will be upgrading the JRE version soon, do you know if we need to recompile the JAR libraries for the new JRE version? Since we don't have the source, is there a 100% accurate decompiler?

Answer 1

No, all JDK versions are backwards-compatible with respect to older jars.

You do not need to recompile.

The only exception to this is if the JAR implements (not uses, but implements) a JDBC driver.