The place to collaborate on an open-sourceimplementation of the Java Platform, Standard Edition, and related projects. (Learn more.)Download and installthe open-source JDK for most popular Linux distributions. Oracle'sfree, GPL-licensed, production-ready OpenJDK JDK 15 binariesare at It basically says that if you need to compile or execute a Java application with an older version of the JDK (for example 1.4 or 1.5), you can do it using the 1.6 because it is backwards compatible. To do it so you will need to add the parameter -source 1.5 and/or -target 1.5 in the javac options or in your IDE.