Interview Questions and Answers for 'Java' | Search Interview Question

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Q701. Difference between Include Directive and include action in jsp

Ans. Include directive includes the file at translation time (the phase of JSP life cycle where the JSP gets converted into the equivalent servlet) whereas the include action includes the file at runtime.

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Q702. Which type of EJB can use bean pooling?

Java EE

Ans. Stateless Session Beans

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Q703. If two Interfaces have same Method, how to handle that Method in a Class implementing these two Interfaces?

Core Java

Ans. It doesn't matter how you define that method in implementing class. there will be only one definition provided and that method can be accessed using reference of either of the interfaces.

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Q704. What are the types of Executor Interfaces ?

Core Java

Ans. Executor - Simple Interface that supports launching new tasks.

ExecutorService - Subinterface of Executor, which adds features that help manage the lifecycle, both of the individual tasks and of the Executor itself.

ScheduledExecutorService - Subinterface of ExecutorService, supports future and-or periodic execution of tasks.

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Q705. how to get most significant bit from a byte?

Core Java

^{This question was recently asked at 'Amazon'.This question is still unanswered. Can you please provide an answer.}

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Q706. Write a program to reverse words of a sentence.

Core Java

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Q707. Given array of integers, find first two numbers that adds up to 10.

Core Java

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Q708. Can we override an abstract method with abstract method in the derived class ?

Core Java

Ans. Yes, but in that case the derived class itself should be abstract. We cannot have an object of a class without definition for the method which has been declared abstract in the parent.

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Q709. Can we override abstract methods ?

Core Java

Ans. Abstract methods are the methods that need to be overridden in the derived class ( either as implementing method or again abstract method ) so it's not only allowed but its required to override abstract method in the derived class.

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Q710. Can we overload abstract methods ?

Core Java

Ans. Yes

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Q711. What is the precedence of operators in Java ?

Core Java

Ans. http://introcs.cs.princeton.edu/java/11precedence/

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Q712. What is Substitutability in Java ?

Core Java

Ans. Substitutability means that the type of the variable does not have to exactly match with the type of the value assigned to that variable. For example - Object reference of Parent object can hold derived object.

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Q713. How do threads share information ?

Core Java

Ans. Through common memory area.

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Q714. write program to do matrix multiplication

Core Java

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Q715. How Marker interfaces works internally ?

Core Java

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Q716. What are some of the Java Naming conventions ?

Core Java

Ans. 1. Class name should be a noun and should start with capital case character.

2. Interface Name should be an adjective and should start with capital case character.

3. Method and Variable names should follow lower camel case notation.

4. package name should be all lower case.

5. constant variables (static final) should be all capital case.

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Q717. What is an execution engine within JVM ?

Core Java

Ans. Execution engine contains interpreter and JIT compiler, which covert byte code into machine code.

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Q718. What access the variable gets if we don't provide any access specifier ?

Core Java

Ans. It gets the default access i.e package protected.

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Q719. How are the concept of Association related to Composition and Inheritance ?

Core Java

Ans. Composition and Inheritance are the different types of Associations for Classes.

Composition is a has-a association between classes.
Inheritance is a is-a association between classes.

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Q720. What are the core OOPs concepts ?

Core Java

Ans. Abstraction, Encapsulation, Polymorphism , Composition and Inheritance

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Q721. Write a method / program that will determine if the parenthesis are balanced in a given string.

Core Java

Ans. https://www.geeksforgeeks.org/check-for-balanced-parentheses-in-an-expression/

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Q722. Why is it important to close files and streams ?

Core Java

Ans. Optimizing Resource utilization. When you open a file using any programming language , that is actually a request to operating system to access the file. When such a request is made , resources are allocated by the OS. When you gracefully close those files, those resources are set free.

In Java if you don’t close the streams and files, Garbage collection identifies the open files which have lost the reference and hence will close them.

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Q723. What is the difference between && and & in Java ?

Core Java

Ans. && is a Logical whereas & is a bitwise operator

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Q724. Why don't Java objects have destructors ?

Core Java

Ans. Java manages memory using built-in garbage collector

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Q725. Write a Java program to print 10 random numbers between 1 to 100?

Core Java

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Q726. Ho do you share / transfer variables between JSP pages ?

Java EE

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Q727. How to find the median number in an array of integers ?

Core Java

Ans.

Arrays.sort(numArray);
double median;
if (numArray.length % 2 == 0)
median = ((double)numArray[numArray.length/2] (double)numArray[numArray.length/2 - 1])/2;
else
median = (double) numArray[numArray.length-1/2];

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Q728. Write a Program to find the missing integer in an array of consecutive numbers?

Core Java

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Q729. Write a Program to validate if a particular character occurs after another in a string

Core Java

Ans. public class Class{
   public static void main(String[] args){
      String str = "xyz123.co@m";

      if(str.indexOf('.') < str.indexOf('@')){
         System.out.println("Not a Valid Email Address");
      }
   }
}

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Q730. Write a Program to validate an email address

Core Java

Ans. public class Class{
public static void main(String[] args){
String str = "xyz@123.com";

if(!str.contains("@") && !str.contains(".") && (str.indexOf('.') < str.indexOf('@'))){
System.out.println("Not a Valid Email Address");
}
}
}

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