Java Interview Questions and Answers

Java Interview Questions and Answers 

Java was developed at SUN MICROSYSTEMS by "JAMES GOSLING" & his team. The trial version was developed and released in the year 1990 was named as "OAK" which was later named as java and it took 18 months to develop scientifically. OAK is the name of a tree. Originally SunMicroSystems is one of the academic university(Stanford University Network).

Core Java Interview Questions and Answers

1) What is the most important feature of java?
A)Java is a platform independent language.


2) What do you mean by platform independent?
A)platform independent means that we can write and compile the java code in one platform (example windows) and can execute the class in any other supported platform example (Linux, Solaris).

3) What is a JVM?
A) JVM is Java Virtual Machine which is a run time environment for the compiled java class files.

4) JVM is platform independent?
A) JVM is not platform independent. JVM is platform specific run time implementation provided by the vendor.

5) What is the difference between a JDK and a JVM?
A) JDK is the Java Development Kit which is for development purpose and it includes execution environment also. But JVM is purely a run time environment and hence you will not be able to compile your source files using a JVM.

6) What is the latest version of Java?

7) What is a JIT compiler?
A) JIT compiler stands for a just-in-time compiler and is a part of JVM which increases the speed of execution of a java program.

8) What is the base class of all java classes?
A) java.lang.Object is the base class of all java classes.

9) Does Java support multiple inheritance?
A) Java doesn’t support multiple inheritances with classes.

10) Are arrays primitive data types?
A)   In Java, arrays are referenced types.

For More click here: Core Java  Interview Questions and Answers


Java String Interview Questions and Answers

1) What is the difference between creating an object of string class using the new operator and using doubles quotes?
A) Using double quotes object of the string class representing a specific sequence of characters could be created only once. Whereas using new operator we can create any number of String class objects representing the same sequence of characters.


Java Exception Handling Interview Questions

1) How many types of errors are there in Java?
A) There are two types of errors are there in Java:
1) Compilation error.
2) Run-time error.

2) What is a compilation Error?
A) Any error that occurs at the time of compilation could be called as Compilation Error.

Java IO Streams Interview Questions


1) What is Stream?

A) A stream is a logical connection between a java program and a File.
                             (or)
A stream can be defined as a continuous flow of data between the java program and persistence media.

2) How many types of Streams are there?
A) There are two types of Streams they are:
1) Input Stream.       
2) Output Stream.

Java Multithreading Interview Questions and Answers


1) Explain about Multitasking?
A) The concept of executing multiple functionalities simultaneously one with the other is known as Multitasking.


2) Explain the advantage of Multitasking?
A) The advantage of multitasking is shown below:
1) BY applying the concept of multitasking we can totally avoid the idle state of the CPU.
2) BY applying the concept of multitasking we can make the functionalities independent on each other.
3) Actually, the concept of multitasking was invented in order to overcome the idle state of CPU. But we apply the concept of multitasking to make the functionalities independent on each other.

Java Constructor Interview Questions and Answers

1) What is Constructor?
A) Constructors are the functionalities which are going to get executed automatically at the time of the creation of an object.
2) What is the difference between Constructor & Methods?
A)      
           Constructor
              Methods
1) With respect to one object, a constructor could be executed only once.
1) With respect to one object, a method could be executed any number of times.
2) Constructors are executed automatically at the time of the creation of an object.
2) A method would be executed only it is explicitly called.
3) A constructor cannot have any return type not even void.
3) A method should and must have a return type at least void is compulsory.
4) Name of the constructor cannot be anything. Name of the constructor should and must be the name of the class.
4) Name of the method can be anything & the name of the method can also be the name of the class.
For More click here: Java Constructor Interview Questions


Java Collection Interview Questions and Answers

1) Is Collection is an Interface or Class?
A) A collection is an Interface.

2) What is the difference between collection and collections?
A) Collection: Collection is an interface in java.util package used to represent a group of as a single entity.

Collections: Collections is a class in java.util package. This class consists exclusively of static methods that operate on or return Collections.
For More click here: Java Collection Interview Questions and Answers



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