Just a correction: they are not separate implementations. Almost all vendors use Oracle's Java implementation -- OpenJDK. It's just that only Oracle and compani

Just a correction: they are not separate implementations. Almost all vendors use Oracle's Java implementation -- OpenJDK. It's just that only Oracle and companies that license the source from Oracle (like Azul) can release non-GPL builds based on OpenJDK, so other vendors maintain old OpenJDK versions by doing their own backporting from the mainline, where most of the work is done by Oracle.