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Interview Questions and Answers - Order By Rating

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 Q941. What is the character limit of url and doesn it apply to GET and POST Requests ?Java EE
Ans. Its 2048 and Yes it applies to get request but not POST. As in Get Request , elements are passed as part of the url, this limit applies to Get requests.

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   Like         Discuss         Correct / Improve     url  internet address

 Q942. In this url

http://javasearch.buggybread.com/InterviewQuestions/questionSearch.php?searchOption=label&keyword=url

What is protocol , domain , path and query param ?		Java EE
Ans. the web URI starts with the protocol which is http in this case, javasearch.buggybread.com is the domain in this case which is a subdomain of buggybread.com, /InterviewQuestions is the path, questionSearch.php is the resource, searchOption and keyword are query params.

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   Like         Discuss         Correct / Improve     url  internet address

 Q943. What is the difference between URI, URL and URN ?Java EE
Ans. URI stands for Uniform Resource Indicator
URL stands for Uniform Resource Locator
URN stands for Uniform Resource Name

URI = URL + URN

For ex - http://javasearch.buggybread.com/InterviewQuestions/questionSearch.php?keyword=url

This is URI. The string from start till .php is URL whereas keyword=url is URN.

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   Like         Discuss         Correct / Improve     url  urn  uri  web address  internet address     Asked in 1 Companies

 Q944. Which is the root interface of Collection classes in Java ?Core Java
Ans. java.util.Collection

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   Like         Discuss         Correct / Improve     collection interface  collections

 Q945. What are the disadvantages of multithreading ?Core Java
Ans. 1. Switching Overheads - Even though multi threading aims at improving performance by reducing the wait time and hence improving overall throughput, there is a cost of switching resources between threads and sometime this cost can surpass the benefits if there isnt much wait for IO or external communication.

2. Debugging is hard with multi threaded code.

3. Deadlock - Execution of multi threaded code many a times lead to deadlock due to shared resources.

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   Like         Discuss         Correct / Improve     multithreading  threads     Asked in 4 Companies

 Q946. What happens to the Exception object after the exception handling is done ?Core Java
Ans. As with all other objects its garbage collected after its usage unless its rethrown.

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   Like         Discuss         Correct / Improve     exceptions  exception handling        rare

 Q947. Why Collection interface does not extend Cloneable interface ?Core Java
Ans. Here is the list of classes that implements Collections Interface - http://www.buggybread.com/2015/02/java-collections-classes-that-implement.html

Having Collection interface to extend Cloneable interface would mean necessarily implement clone method by all implementing classes. As not all collection classes allow duplicate elements, it makes no sense to clone elements for them.

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   Like         Discuss         Correct / Improve     cloneable  collections  collection interface  cloning

 Q948. What are the benefits of Enums ?Core Java
Ans. Enums in Java are used to declare predefined objects and then reuse them. they offer many benefits

1. Enum instance are type safe and thread safe.

2. Enum instances are singleton and hence reused.

3. If we use Enums with Switch , It makes sure that the passed argument is either of its instance and hence provides a safeguard.

4. If we use Enum with Sorted Collections we can sort the elements with a predefined priorities ( as per constant declaration in enum )

5. We can use Enum as a Factory by defining its constructor.

6. We can store related constant data within enum. For example - If we know the values for the map upfront, we can alternatively use an enum.

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 Q949. What is System.in in Java ?Core Java
Ans. It is an InputSream which is usually connected to the keyboard input of console program.

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   Like         Discuss         Correct / Improve     System.in  Input Stream  Input Output

 Q950. How is == operator different for objects and primitive types ? Core Java
Ans. For objects or references, == operator check if the reference on left and right points to the same object.

For primitive types or variables, == operator check if the variable on left and right holds the same value.

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   Like         Discuss         Correct / Improve     ==  object equality  operator      Basic

 Q951. What is the difference between = and == in Java ?Core Java
Ans. = is the assignment operator that assigns the result of the expression on the right to the variable on the left, whereas

== is the operator to check object equality to see if the reference on left and right are pointing to the same object. For primitive types, its used to check if both variables holds the same value.

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   Like         Discuss         Correct / Improve     =  ==  assignment operator  object equality  difference between      Basic

 Q952. What is a classpath in Java ?Core Java
Ans. Classpath is the parameter for JVM to look for java classes ( .class files ) that are to be looad by class loader

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   Like         Discuss         Correct / Improve     classpath     Asked in 1 Companies      basic

 Q953. What is meant by size and index of a collection ?Core Java
Ans. As the name suggest size is the size of collection / data structure i.e number of elements or memory utilized by the collection.

Index is the position of an element in a collection or data structure.

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   Like         Discuss         Correct / Improve     collection  index of collection  size of collection      Basic

 Q954. Difference between multiple and multi level inheritance ?Core Java
Ans. Multiple Inheritance refers to the concept of a class inheriting multiple classes. Example - Class C extends Class A ,Class B. This is not allowed in Java.

Multilevel Inheritance refers to the concept of Inheritance in a chain. Example - Class B extends Class A, Class C extends Class B. This is permitted in Java.

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   Like         Discuss         Correct / Improve     inheritance  object oriented programming (oops)  oops concepts   multiple inheritance  object oriented programming (oops)  oops concepts   multi level inheritance  object oriented programming (oops)  oops concepts      Basic        frequent

 Q955. Where do we generally use comparable interface ?Core Java
Ans. Implementing Comparable interface means that the elements of the class are comparable i.e the class provides the implementation of compareTo method that would help comparing the elements.

This is usually required if we are planning to sort elements of a collection, If compareTo method is not defined , the sorting class / method could never understand a way to compare its elements in order to sort them.

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 Q956. How and when the Buffer is cleared when using Buffered Writer Classes ?Core Java
Ans. Buffer is cleared in 2 circumstances, i.e 1. naturally when the buffer is filled and 2. explicitly when the method flush is called ( for flushing the residual )

Ideally we just need to call flush once at the end of file writing so that the residual content should be dumped to file.

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   Like         Discuss         Correct / Improve     BufferedWriter  Writer  PrintWriter  File io  flush  file handling

 Q957. What is IdentityHashMap ?Core Java
Ans. IdentityHashMap is a class that implements AbstractMap and provides a data structure with Elements having Key Value pair, just like HashMap. It is similar to HashMap except that it uses reference equality when comparing elements.

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   Like         Discuss         Correct / Improve     IdentityHashMap  map  hashmap  collections

 Q958. Do we need to implement all interface methods if a class is implementing it ?Core Java
Ans. Yes, a Class is supposed to define all abstract methods declared in the interface. With Java 8 , Interfaces can have default methods which need not be implemented by the implementing class.

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 Q959. Can we access private members of the parent class ? i.e Are private members of the class visible in the derived class ?Core Java
Ans. No, If both Parent and Derived are outer classes.

public class Vehicle {
private static String manufacturingDate = "2016";
}

public class Car extends Vehicle{
public static void main(String args[]){
System.out.println(manufacturingDate); // error - The field Vehicle.manufacturingDate is not visible
}
}

Yes, If derived is the inner class of Parent.

public class Vehicle {
private static String manufacturingDate = "2016";
static public class Car extends Vehicle{
public static void main(String args[]){
System.out.println(manufacturingDate); // no problem
}
}
}

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   Like         Discuss         Correct / Improve     private members   private methods   private variables   inheritance  object oriented programming (oops)  oops concepts   members visibility   inner classes  nexted classes      basic        frequent

 Q960. Are Strings objects in Java ?Core Java
Ans. Yes, everything except primitive types are objects in Java.

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 Q961. Does an ArrayList allow elements of different types ? If not, Why the following code works List list1 = new ArrayList<>(); list1.add(1); list1.add("1");Core Java
Ans. With Java 7 or Later. If you don't declare the list to be of specific type , it treats it as list of objects. int 1 is auto boxed to Integer and "1" is String and hence both are objects.

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   Like         Discuss         Correct / Improve     arraylist  list  collections

 Q962. 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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   Like         Discuss         Correct / Improve     if statement  control statements  == and equals  ==  .equals   code optimization
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 Q963. 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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 Q964. 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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   Like         Discuss         Correct / Improve     main method   main method visibility      basic
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Rarely asked as it was introduced with Java 8.
 Q965. 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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   Like         Discuss         Correct / Improve     :: operator   lambda expression  java 8

 Q966. 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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   Like         Discuss         Correct / Improve     default methods  java 8  multiple inheritance  object oriented programming (oops)  oops concepts  diamond problem   interfaces

 Q967. What are the different uses of Interfaces in Java ?Core Java
Ans. 1. Regulation / Enforcement / Policy / Contract , It's primary use

2. Use as a collection of utility methods(since java 8 through default methods)

3. Collecting constants together, As Interface are lighter, it makes sense to use them instead of classes if no getters and setters required.

4. Creation of Custom Annotations

5. Special services like marker interface

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 Q968. 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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 Q969. 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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   Like         Discuss         Correct / Improve     static   static variables   class level variables     Asked in 1 Companies      basic        frequent
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 Q970. Can I run a java program without creating any class ?
Ans. No, It requires creation of atleast one Class. Creating an object of that class is not compulsory as we can write all our logic within main method which is static.

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