Core Java Interview Questions

What is Core java?

Core Java” is Sun’s term, used to refer to Java SE, the standard edition and a set of related technologies, like the Java VM, CORBA, et cetera. This is mostly to differentiate from, say, Java ME or Java EE. Also note that they’re talking about a set of libraries rather than the programming language.

What is core java and advanced java?

Core java is used for developing general java application where as Advanced java is used for developing the web based application and enterprise application. Core java is having the concept of Java Fundamentals, Applet, Swings, JDBC, Java Beans. I thought swing was a part of advanced java

What are the important features of Java 8 release?

Java 8 has been released in March 2014, so it’s one of the hot topic in java interview questions. If you answer this question clearly, it will show that you like to keep yourself up-to-date with the latest technologies.
Java 8 has been one of the biggest releases after Java 5 annotations and generics. Some of the important features of Java 8 are:
Interface changes with default and static methods
Functional interfaces and Lambda Expressions
Java Stream API for collection classes
Java Date Time API

What is difference between JDK, JRE and JVM?

JVM
JVM is an acronym for Java Virtual Machine, it is an abstract machine which provides the runtime environment in which java byte code 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.

What do you mean by platform independence of Java?

Platform independence means that you can run the same Java Program in any Operating System. For example, you can write java program in Windows and run it in Mac OS.

How many types of memory areas are allocated by JVM?

Many types:
Class (Method) Area
Heap
Stack
Program Counter Register
Native Method Stack

What is JVM and is it platform independent?

Java Virtual Machine (JVM) is the heart of java programming language. JVM is responsible for converting byte code into machine readable code. JVM is not platform independent, that’s why you have different JVM for different operating systems. We can customize JVM with Java Options, such as allocating minimum and maximum memory to JVM. It’s called virtual because it provides an interface that doesn’t depend on the underlying OS.

What is JIT compiler?

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.

What is the difference between JDK and JVM?

Java Development Kit (JDK) is for development purpose and JVM is a part of it to execute the java programs.

JDK provides all the tools, executables and binaries required to compile, debug and execute a Java Program. The execution part is handled by JVM to provide machine independence.

What is platform?

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.

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