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 Q461. Write a program to calculate factorial of a number using recursionCore Java
Ans.

public class Factorial {
   public static void main(String[] args){
      int x = 5;
      
      System.out.println(calculateFactorial(x));
   
   }
   
   private static int calculateFactorial(int x){
      if(x==1){
         return 1;
      }
      return x * calculateFactorial(x-1);
   }
}

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   Like         Discuss         Correct / Improve     factorial  calculate factorial  code  coding  recursion     Asked in 1 Companies      basic

 Q462. Write code for constructor overloadingCore Java
Ans. http://javasearch.buggybread.com/CodeSnippets/searchCodeSamples.php?&category=code&searchOption&keyword=965

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 Q463. In the following code , how many methods needs to be implemented in Class B ?

public interface A{
   public void method1();
   public void method2();
   public void method3();
}

abstract class B implements A{
}		Core Java
Ans. As Class B has been declared abstract , we can either implement any of these methods and just declare rest of them abstract.

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 Q464. What will the following code print ?

Integer a = 100, b =100;
Integer c = 1000, d = 1000;
System.out.println(a == b);
System.out.println(c ==d);		Core Java
Ans. false
false

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   Like         Discuss         Correct / Improve     object equality  code  coding        frequent

  Q465. How is multiple inheritance implemented in Java ?Core Java
Ans. There was no multiple inheritance in java before version 8 as implementing multiple interfaces cannot be termed as inheritance.

With Java 8 , came the concept of default methods wherein the class implementing the interface carries the default implementation from the interface and hence facilitating multiple inheritance.

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  Q466. What is a Destructor ? Do we have Destructors in Java ?Core Java
Ans. Destructor is used to de-allocate memory allocated by objects.

There are no destructors in Java. Alternatively, Java provides Automatic garbage collection i.e automatically releasing the un-referenced memory.

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Frequently asked.
 Q467. What should a class do if its implementing an interface ?Core Java
Ans. It should either implement all interface methods or declare unimplemented methods as abstract.

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 Q468. What should a class do if its extending an abstract class ?Core Java
Ans. It should either implement the abstract methods or re-declare them abstract.

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   Like         Discuss         Correct / Improve     abstract class     Asked in 2 Companies      Basic        Frequent

 Q469. What is Associativity while evaluating a Java statement ?Core Java
Ans. Associativity determines whether an expression is evaluated left-right or right-left. When an expression has two operators with the same precedence, the expression is evaluated according to its associativity.

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 Q470. What is the difference between following time formats ?

hh:mm:ss
HH:mm:ss
kk:mm:ss
KK:mm:ss		Core Java
Ans. hh= hours in 1-12 format
HH= hours in 0-23 format
kk = Hours in 1-24 format
KK= hours in 0-11 format

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 Q471. Write a java program to implement Quick sort ?Core Java
Ans. http://www.programcreek.com/2012/11/quicksort-array-in-java/

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Frequently asked to Fresh graduates.
 Q472. Write a program to implement Binary search ?Core Java
Ans. http://algs4.cs.princeton.edu/11model/BinarySearch.java.html

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 Q473. Which data structure would you recommend for ordered and sorted data?Core Java
Ans. TreeSet and TreeMap are used for maintaining sorted elements.

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 Q474. Explain Exception Hierarchy in Java SE ?Core Java
Ans. <a href="http://www.programcreek.com/2009/02/diagram-for-hierarchy-of-exception-classes/" rel="nofollow">http://www.programcreek.com/2009/02/diagram-for-hierarchy-of-exception-classes/</a>

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 Q475. Can we have try statement without catch? If try statement contains return will the finally block be executed? What happens if there is an exception inside finally block?Core Java
Ans. Yes, with finally.

Yes, finally block will be executed even if there is no exception in try block.

If finally throws an exception, the exception gets thrown to the calling module.

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   Like         Discuss         Correct / Improve     exception handling     Asked in 1 Companies      intermediate

Very Frequently asked to fresh graduates and less experienced.
 Q476. What are the principle concepts of Object Oriented Programming ?Core Java
Ans. Abstraction Polymorphism Inheritance Encapsulation

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 Q477. In case of a synchronized method, Does the method only gets locked or the whole object ?Core Java
Ans. Just the method gets locked.

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 Q478. Can you assign value to a static final type at runtime ?Core Java
Ans. No

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All these acronyms JDK,JRE,JVM etc are very frequently asked.
 Q479. Difference between JDK and JRE ?Core Java
Ans. JRE or Java Runtime Environment is the Java Virtual Machine on which class files are executed. It includes borwser plugins that facilitates execution of class files in browsers.

JDK or Java Development Kit includes JRE , compiler and development tools.

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 Q480. Is New Keyword a method Name ?Core Java
Ans. No, Its an Operator.

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 Q481. What are the disadvantages of running multiple apps in single JVM ?Core Java
Ans. 1. Issue with Jar and ClassPath Conflicts

2. Killing JVM will terminate all applications

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 Q482. How does the String Class stores the string in memory ?Core Java
Ans. It stores the string as a character array with 2 bytes for each character.

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 Q483. What is multilevel inheritance ?Core Java
Ans. Multi Level Inheritance is multi level hierarchy of classes. Here is the example - http://www.buggybread.com/2015/09/java-se-class-diagram-classes-that_603.html

Class RoleList extends ArrayList which in turn extends AbstractList which in turn extends AbstractCollection.

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 Q484. What is a static variable in Java ?Core Java
Ans. It is a class level variable that is shared among the objects of that class.

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 Q485. What is the difference between constructor and instance initialization blocks ?Core Java
Ans. Constructor has the same name as class name whereas instance initialization block just have a body without any name or visibility type.

instance initialization blocks are useful if we want to have some code run regardless of which constructor is used or if we want to do some instance initialization for anonymous classes.

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 Q486. Does default methods introduce multiple inheritance and the Diamond problem in Java 8 ?Core Java
Ans. Default methods results in multiple inheritance of behavior and not of state. In case we try to implement multiple interfaces with default method having same name and signature, and don't override it in implementation class, it will throw an error.

For example -

interface MyInterface {
public void default myMethod(){
}
}

interface MyInterface2 {
public void default myMethod(){
}
}

class MyClass implements MyInterface,MyInterface2 {
}

This code will compilation error "Duplicate Default Method"

if we specify the definition of myMethod() in myClass, compiler won't complain and there is no conflict and MyClass can use overridden definition. But if we don't override myMethod() in MyClass, Java would be in conflict as to what definition should be carried to MyClass and hence throws compilation error.

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Rarely asked as it was introduced with Java 8.
 Q487. What is the use of :: operator wef from Java 8 ?Core Java
Ans. We can refer to a function using this operator like System.out.println(intList.stream().reduce(Math::max).get());

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 Q488. Can we declare the main method as private ?Core Java
Ans. Yes, compiler won't complain but at runtime it will give an error saying "Error: Main method not found in class". Even though we can use this method as any other private method, it cannot be invocate by executing the class.

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 Q489. What is wrong with the following if statement ?

if(x==y && x.equals(y) {
}		Core Java
Ans. x==y means that both references have same type and are pointing to same memory location and hence would always mean that they have same value.

x.equals(y) is not required in this case.

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 Q490. What is wrong with the following if statement ?

if(x==y || x.equals(y) {
}		Core Java
Ans. if x==y turns out to be true x.equals(y) will be true too. If x.equals(y) could be true even if x==y is true or not.

So the only possible outcomes are

1 || 1 = 1
0 || 1 = 1
0 || 0 = 0

i.e the outcome of x.equals(y)

check for x==y is not required in this if statement.

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