JDK Java developer kit contains
tools like
1.
Javac - compiler to convert source to byte code
2.
Java - Interpreter to execute the byte code and
produces the output
3.
Javadoc - to generate java documentation
4.
Jar - tool to work with jar and war files
5.
Javap - java decompile
Java Runtime Environment
JRE Java Runtime environment contains
tools to execute a bytecode
1.
Java - Interpreter
You can't see any tools regarding development in JRE, ex Javac, jar, javap will be missing in JRE
JDK will comes with its one copy of
private JRE to execute the byte code.
What do we need JDK
or JRE?
Java can be downloaded as JDK or
JRE based on your need,
1.
If you are developer you should have a JDK installed
to compile your source code
2. If you just need to run the java application that was already complied you can have JRE alone installed.