The Java Development Kit (JDK) is a set of utilities that allow one to create software systems for the Java platform. It consists of several tools, including the following:
java- the Java virtual machine
javac- a Java compiler
javadoc- generates HTML documentation from special comments in Java source files
javap- disassembles Java class files into their bytecode instructions
jar- generates Java Archive files, or JAR files, a collection of Java class files
It also comes with the standard Java API class library. Besides the above tools, there are a lot more.