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

Interview Questions and Answers - Order By Rating

Q1391. What will happen if there is a default method conflict as mentioned above and we have specified the same signature method in the base class instead of overriding in the existing class ?

Ans. There won't be any problem as the Base class method will have precedence over the Interface Default methods.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java java8 default methods}

Q1392. If a method definition has been specified in Class , its Base Class , and the interface which the class is implementing, Which definition will be picked if we try to access it using Interface Reference and Class object ?

Ans. Class method definition is overriding both the definitions and hence will be picked.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java java8 default methods}

Q1393. If a method definition has been specified in the Base Class and the interface which the class is implementing, Which definition will be picked if we try to access it using Interface Reference and Class object ?

Ans. Base Class Definition will have precedence over the Interface Default method definition.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java java8 default methods}

Q1394. Can we use static method definitions in Interfaces ?

Core Java

Ans. Yes, Effective Java 8.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java java8 static interface methods yes-no Asked in 1 Companies}

Q1395. Can we access Interface static method using Interface references ?

Ans. No, only using Interface Name.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java java8 static interface methods}

Q1396. Can we have default method with same name and signature in the derived Interface as the static method in base Interface and vice versa ?

Ans. Yes , we can do that as static methods are not accessible using references and hence cannot lead to conflict. We cannot do inverse as Default methods cannot be overridden with the static methods in derived interface.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java java8 default methods static interface methods}

Frequently asked at Manhattan Associates ( Based on 2 feedback )

Q1397. What is a Lambda Expression ? What's its use ?

Core Java

Ans. Its an anonymous method without any declaration.

Lambda Expression are useful to write shorthand Code and hence saves the effort of writing lengthy Code.

It promotes Developer productivity, Better Readable and Reliable code.

Sample Code for lambda

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java java8 lambda expression architecture Asked in 58 Companies expert frequent}

Try 1 Question(s) Test

Q1398. Difference between Predicate, Supplier and Consumer ?

Core Java

Ans. Predicate represents an anonymous function that accepts one argument and produces a result.

Supplier represents an anonymous function that accepts no argument and produces a result.

Consumer represents an anonymous function that accepts an argument and produces no result.

Sample Code for Predicate

Sample Code for Supplier

Sample Code for Consumer

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java java8 predicate consumer supplier lambda expression predicate vs consumer vs supplier expert}

Q1399. What does the following lambda expression means ?

helloJava8 ( x-> x%2 )

Ans. helloJava8 receives an Integer as argument and then returns the modulus of that Integer.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java java8 lambda expression}

Q1400. Write a program to see if the number is perfect number or not ?

Core Java

Ans. http://www.c4learn.com/c-programs/program-to-check-whether-number-is.html

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java at&t coding}

Q1401. Difference between a Pointer and a Reference ?

Ans. We can't get the address of a reference like a pointer. Moreover we cannot perform pointer arithmetic with references.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java pointer reference at&t}

Q1402. Difference between TCP and UDP ?

Networking

Ans. http://www.cyberciti.biz/faq/key-differences-between-tcp-and-udp-protocols/

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java network programming architecture Cloud Computing Google Cloud Computing (GCP) Amazon Web Services (AWS) Asked in 3 Companies}

Q1403. What things you would care about to improve the performance of Application if its identified that its DB communication that needs to be improved ?

Solution

Ans. 1. Query Optimization ( Query Rewriting , Prepared Statements )

2. Restructuring Indexes.

3. DB Caching Tuning ( if using ORM )

4. Identifying the problems ( if any ) with the ORM Strategy ( If using ORM )

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java db database hibernate orm at&t overstock.com performance improvement architecture technical lead architect intermediate}

Very frequently asked. Usually followed by questions related to private constructor and synchronized access. Frequently asked in JPMorgan and TCS (Based on 2 feedback)

Q1404. Explain Singleton Design Pattern ?

Design

Ans. http://www.buggybread.com/2014/03/java-design-pattern-singleton-interview.html

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java design pattern singleton at&t ebay fidelity india united healthcare india Asked in 46 Companies intermediate frequent}

Q1405. If I try to add Enum constants to a TreeSet, What sorting order will it use ?

Ans. Tree Set will sort the Values in the order in which Enum constants are declared.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java collections set treeset enum sorting technical lead}

Q1406. Can we override compareTo method for Enumerations ?

Core Java

Ans. No. compareTo method is declared final for the Enumerations and hence cannot be overriden. This has been intentionally done so that one cannot temper with the sorting order on the Enumeration which is the order in which Enum constants are declared.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java compareto final methods enum enumeration expert}

Q1407. When does an application throw NullPointerException ?

Core Java

Ans. When it tries to access an object element or method using reference which is actually null.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve exceptions npe nullpointerexception Asked in 1 Companies basic frequent}

Q1408. What are the conventions regarding constant variables or static final variables ?

Core Java

Ans. They should be named all in upper case with underscore separating words.

Moreover the name should be such that it identifies the value. For example, if we are using constant for employee Id 123, it should be named something like EMPLOYEE_ID_123 and not EMPLOYEE_ID

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve constants variable names java conventions}

Q1409. How do you define a class of constants in Java?

Ans. Make the class as final.
Disable the object construction by making constructor private.
Keep only Static Final Variables declared and Defined at the same time.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java constants constant class java}

Q1410. What are the steps to be performed while coding Junit with Mocking framework ?

JUnit

Ans. Initialize required objects for working with mocks and tested method
Set the mock behaviour on dependent objects
Execute the tested method
Perform assertions
Verify if a method is invoked or not

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve junit mocking frameworks mock unit testing java white box testing Mockito}

Q1411. What will be the output of this code ?

Set mySet = new HashSet();
mySet.add("4567");
mySet.add("5678");
mySet.add("6789");
for(String s: mySet){
System.out.println(s);
}

Ans. It will print 4567,5678 and 6789 but Order cannot be predicted.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java collections set hashset coding code}

Try 1 Question(s) Test

Q1412. What will be the output of this code ?

Set mySet = new TreeSet();
mySet.add("4567");
mySet.add("5678");
mySet.add("6789");
for(String s: mySet){
System.out.println(s);
}

Ans. 4567
5678
6789

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java collections set treeset coding code}

Q1413. What will be the output of this code ?

Set mySet = new HashSet();
mySet.add("4567");
mySet.add("5678");
mySet.add("6789");
System.out.println(s.get(0));

Ans. This will give compile time error as we cannot retrieve the element from a specified index using Set. Set doesn't maintain elements in any order.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java collections set hashset coding code}

Try 1 Question(s) Test

Q1414. What will be the output of the following code ?

enum Day {
   MONDAY,TUESDAY,WEDNESDAY,THURSDAY,FRIDAY,SATURDAY,SUNDAY
}

public class BuggyBread1{
   public static void main (String args[]) {
      Set mySet = new HashSet();
      mySet.add(Day.SATURDAY);
      mySet.add(Day.WEDNESDAY);
      mySet.add(Day.FRIDAY);
      mySet.add(Day.WEDNESDAY);
      for(Day d: mySet){
         System.out.println(d);
      }
   }
}

Ans. FRIDAY , SATURDAY and WEDNESDAY will be printed but the order cannot be determined.

Only one FRIDAY will be printed as Set doesn't allow duplicates. Order cannot be determined as HashSet doesn't maintain elements in a particular order.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java code coding enum set hashset}

Try 3 Question(s) Test

Q1415. What will be the output of the following code ?

enum Day {
MONDAY,TUESDAY,WEDNESDAY,THURSDAY,FRIDAY,SATURDAY,SUNDAY
}

public class BuggyBread1{
public static void main (String args[]) {
Set mySet = new TreeSet();
mySet.add(Day.SATURDAY);
mySet.add(Day.WEDNESDAY);
mySet.add(Day.FRIDAY);
mySet.add(Day.WEDNESDAY);
for(Day d: mySet){
System.out.println(d);
}
}
}

Core Java

Ans. WEDNESDAY
FRIDAY
SATURDAY

Only one FRIDAY will be printed as Set doesn't allow duplicates.Elements will be printed in the order in which constants are declared in the Enum. TreeSet maintains the elements in the ascending order which is identified by the defined compareTo method. compareTo method in Enum has been defined such that the constant declared later are greater than the constants declared prior.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java code coding enum set treeset advanced}

Try 3 Question(s) Test

Q1416. public class BuggyBread1{

public static void main (String args[]) {
Set<String> mySet = new TreeSet<String>();
mySet.add(""1"");
mySet.add(""2"");
mySet.add(""111"");
for(String d: mySet){
System.out.println(d);
}
}
}

Core Java

Ans. 1
111
2

TreeSet maintains the elements in the ascending order which is identified by the compareTo method. compareTo method in String has been defined such that it results in the natural alphabetic Order. Here the elements in the TreeSet are of String and not of Integer. In String Natural Order, 111 comes before 2 as ascii of 1st character first determines the order.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java code coding set treeset string integer}

Q1417. public class BuggyBread1{

public static void main (String args[]) {
Set<Integer> mySet = new TreeSet<Integer>();
mySet.add(1);
mySet.add(2);
mySet.add(111);
for(Integer d: mySet){
System.out.println(d);
}
}
}

Core Java

Ans. 1
2
111

TreeSet maintains the elements in the ascending order which is identified by the compareTo method. compareTo method in Integer has been defined such that it results in the natural numerical Order.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java code coding set treeset}

Q1418. Can we extend an Enum ?

Core Java

Ans. No. Enums are final by design.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java enums inheritance object oriented programming (oops) oops concepts yes-no Asked in 1 Companies intermediate}

Q1419. How can we change the JDK compliance level ?

Eclipse

Ans. Windows -> Preferences -> Java - Compiler -> Java Compliance Level

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve eclipse jdk compliance level eclipse java}

Q1420. Can I use different Java versions for building different Eclipse projects ?

Eclipse

Ans. Yes. We can assign different JRE System libraries by going to

Java Build Path -> Libraries

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java eclipse jre library}

Search Interview Questions

Help us and Others Improve. Please let us know the questions asked in any of your previous interview.