JVM has a method area common across all the threads. It contains per-class elements like constant pool, fields, method local data, method code, constructor codes etc. which are used in class and initialization of objects/interfaces.This method area gets created during JVM start-up. It is generally part of Heap area. It could be of fixed size or vary. Its memory may not be contiguous. JVM implementation can give control to programmer over Method area creation, its sizing etc. If method area memory is not sufficient to satisfy an allocation request then JVM throws OutOfMemoryError.

Java memory model is divided between Thread Stacks (One for each thread) and a heap area.Thread Stack: It is a thread specific memory area and contains local variables, methods call information etc. JVM stacks could be of fixed size or variable size. If computation in a thread exceeds its stack size limit then JVM throws StackOverflowError and exits.HeapIt contains all the objects created during application lifecycle. The heap is created when the virtual machine starts up. Garbage collector reclaims heap storage for objects and objects are never explicitly deallocated. The JVM is not using any automatic storage management system, and ... Read More

JRE is Java Runtime Environment and is the machine-specific implementation of JVM. It contains libraries like rt.jar, class loaders etc which are used by JVM.

JDK, contains development tools and JRE.

Assuming you have installed Java in \usr\local\java\jdk directory −if you use bash as your shell, then you would add the following line to the end of your '.bashrc: export JAVA_HOME=\usr\local\java\jdk'Assuming you have stored your Java programs in \usr\local\myprograms\ directory −if you use bash as your shell, then you would add the following line to the end of your '.bashrc: export CLASSPATH=\usr\local\myprograms'.

Set pathAssuming you have installed Java in c:\Program Files\java\jdk directory −Right-click on 'My Computer' and select 'Properties'.Click the 'Environment variables' button under the 'Advanced' tab.Now, alter the 'Path' variable so that it also contains the path to the Java executable. Example, if the path is currently set to 'C:\WINDOWS\SYSTEM32', then change your path to read 'C:\WINDOWS\SYSTEM32;c:\Program Files\java\jdk\bin'.Set ClasspathAssuming you have stored your Java programs in c:\myprograms\ directory −Right-click on 'My Computer' and select 'Properties'.Click the 'Environment variables' button under the 'Advanced' tab.Now, add the 'CLASSPATH' variable and set the path to the c:\myprograms\'.Read More

Assuming you have installed Java in \usr\local\java\jdk directory −if you use bash as your shell, then you would add the following line to the end of your '.bashrc: export JAVA_HOME=\usr\local\java\jdk'

Assuming you have installed Java in \usr\local\java\jdk directory −if you use bash as your shell, then you would add the following line to the end of your '.bashrc: export JAVA_HOME=\usr\local\java\jdk'

Assuming you have installed Java in c:\Program Files\java\jdk directory −Right-click on 'My Computer' and select 'Properties'.Click the 'Environment variables' button under the 'Advanced' tab.Now, add the 'JAVA_HOME' variable and set the path to the c:\Program Files\java\jdk'.

Environment variable PATH should be set to point to where the Java binaries have been installed. Refer to your shell documentation if you have trouble doing this.Example, if you use bash as your shell, then you would add the following line to the end of your '.bashrc: export PATH=/path/to/java:$PATH'