Core Java Interview Question

1. What is JVM ?

Java virtual Machine(JVM) is a virtual Machine that provides runtime environment to execute java byte code. The JVM doesn't understand Java type, that's why you compile your *.java files to obtain *.class files that contain the byte codes understandable by the JVM.

Read more about JVM here.

2. What is JIT ?

JIT is the part of the Java Virtual Machine (JVM)that is used to speed up the execution time. JIT Compiler compiles parts of byte code that have similar functionality at the same time and hence reduces the amount of time needed.

3.What is JRE?

JRE stands for Java Runtime Environment which is used to provide an environment at runtime. It contains set of supporting libraries in combination with core classes and various other files that are used by JVM at runtime. JRE is a part of JDK (Java Development Toolkit) but can be downloaded separately.

4.What is JDK?

JDK (Java SE Development Kit) provides the environment to develop and execute(run) the Java program. JDK is a kit which includes two things  :

• Development Tools(to provide an environment to develop your java programs)
• JRE (to execute your java program).

5. What is Garbage Collector?
Garbage Collector is the process of Java program which runs in the background along with regular Java program to collect unused memory space for improving the performance of our applications.

Read more about Garbage Collector here

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