Sec 1: Basics of Java Questions
Last updated
Last updated
JVM JVM is an acronym for Java Virtual Machine, it is an abstract machine which provides the runtime environment in which java bytecode can be executed. It is a specification. JVMs are available for many hardware and software platforms (so JVM is platform dependent).
JRE JRE stands for Java Runtime Environment. It is the implementation of JVM.
JDK JDK is an acronym for Java Development Kit. It physically exists. It contains JRE + development tools.
Just-In-Time(JIT) compiler:It is used to improve the performance. JIT compiles parts of the byte code that have similar functionality at the same time, and hence reduces the amount of time needed for compilation.Here the term “compiler” refers to a translator from the instruction set of a Java virtual machine (JVM) to the instruction set of a specific CPU.
A platform is basically the hardware or software environment in which a program runs. There are two types of platforms software-based and hardware-based. Java provides software-based platform.
The Java platform differs from most other platforms in the sense that it's a software-based platform that runs on top of other hardware-based platforms.It has two components:
Runtime Environment
API (Application Programming Interface)
The bytecode. Java is compiled to be a byte code which is the intermediate language between source code and machine code. This byte code is not platform specific and hence can be fed to any platform.
The classloader is a subsystem of JVM that is used to load classes and interfaces.There are many types of classloaders e.g. Bootstrap classloader, Extension classloader, System classloader, Plugin classloader etc.
No.
It is empty. But not null.
Program compiles and runs properly.
The local variables are not initialized to any default value, neither primitives nor object references.
Yes, save your java file by .java only, compile it by javac.java and run by java yourclassname
