Is Java Platform Independent if yes then how?

Yes, Java is a Platform Independent language. Unlike many programming languages javac compiles the program to form a bytecode or .class file. This file is independent of the software or hardware running but needs a JVM(Java Virtual Machine) file preinstalled in the operating system for further execution of the bytecode.
Although JVM is platform dependent, the bytecode can be created on any System and can be executed in any other system despite hardware or software being used which makes Java platform independent.