use of jdk jre and jvm code example

Example: JDK JRE JVM

Java Virtual Machine: JVM is an abstract machine. 
It actually runs by Java code. Most people know Java with this slogan 
"Write once and run everywhere' This slogan is because of JVM. 
• Java Runtime Environment : JRE is what we need to run a Java program 
and containsset of libraries and other files that JVM uses at run time. 
JRE = JVM + Library Classes 
• Java Development Kit : JDK is what we need to compile Java source code 
and contains JRE, development tools. JDK = JRE + Development tools