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

Interview Questions and Answers - Order By Newest

Q1231. What is string pool and what is the use of intern() function ?

Ans. The Java String class intern() method returns the interned string. It returns the canonical representation of string.

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

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1232. What is Throwable ?

Core Java

Ans. Throwable in java is a class that is the superclass of all exceptions and errors which may occurs in java program.It extends obcect class.

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

_{Like Discuss Correct / Improve exception handling throwable Asked in 1 Companies basic}

Q1233. Hash map using/without using Java 8

Core Java

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

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

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1234. Can we assign the reference to this variable ?

Core Java

Ans. No

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

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1235. What are different types of Polymorphism in Java ?

Core Java

Ans. run time polymorphism
compile time polymorphism

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

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1236. Is String mutable or immutable in Java ?

Core Java

Ans. String is Immutable because of String Constant Pool.

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

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1237. Explain Collections in Java

Core Java

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

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

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1238. Should we do anything to avoid memory leaks in Java ?

Core Java

Ans. Java has a intrinsic way of checking leaks and reclaiming memory called garbage collection. Moreover Java doesn't support pointer arithmetics , so there is very low comparative chance of memory leaks, compared to C,C++

Though there may be tools that may audit code to make sure that we are not leaving much for the garbage collection to work but I have never heard anyone doing anything for memory leaks in Java.

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

_{Like Discuss Correct / Improve memory leak in java}

Q1239. Write a Program to draw a fish ?

Core Java

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

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

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1240. What is the use of defining equals , compareTo and hashcode methods in a class ? Where are they used ?

Core Java

Ans. equals, compareTo and hashcode are of use when the objects are used within collections.

Equals helps with collections that helps maintaining only unique objects ( like Set )

compare and compareTo helps with collections that helps maintaining objects in order ( TreeSet, TreeMap etc )

hascode helps with collections that facilitates hash searching ( like hashSet, hashMap etc )

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

_{Like Discuss Correct / Improve equals compareTo hashcode method}

Q1241. Write a program to make an array act as a set.

Core Java

Ans. public Set convertArrayToList(T array[]) {
Set set = new HashSet<>(Arrays.asList(array));
return set;
}

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

_{Like Discuss Correct / Improve arrays collections set Asked in 1 Companies}

Q1242. What are the advantages and disadvantages of Lambda Expression ?

Core Java

^{This question was recently asked at 'Number 8'.This question is still unanswered. Can you please provide an answer.}

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

_{Like Discuss Correct / Improve java8 java 8 java lambda expressions Asked in 1 Companies}

Q1243. Can the value of a static variable be changed ?

Core Java

Ans. Yes the value of a static variable can be changed. It's the final keyword that restrict the modification of value not static.

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

_{Like Discuss Correct / Improve static variables}

Q1244. Why wait(), notify(), notifyAll() methods are in Object class instead of Thread class?

Core Java

Ans. wait() and notify() methods are defined in Object class rather than Thread class.If wait() and notify() were on the Thread instead then each thread would have to know the status of every other thread and there is no way to know thread1 that thread2 was waiting for any resource to access.Hence, notify, wait, notifyAll methods are defined in object class in Java.

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

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1245. How can we create an arraylist of unique values ?

Core Java

Ans. We can put the value in a set to enforce uniqueness and then dum those value into an arraylist.

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

_{Like Discuss Correct / Improve arraylist design collections}

Q1246. Interface vs Abstraction

Core Java

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

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

_{Like Discuss Correct / Improve interface vs abstraction interfacing vs abstraction relation between interface and abstraction How interface provide abstraction Asked in 1 Companies}

Q1247. What is the different between collection and Stream Api ?

Core Java

Ans. data under collection are actually stored in memory so that they can be retrieved when needed whereas data in streams are not stored and hence we need to construct it again when needed.

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

_{Like Discuss Correct / Improve collection classes stream api collection vs stream Asked in 1 Companies}

Q1248. What are the benefits of Java over other Programming Languages ?

Core Java

Ans. 1. JVM that makes it platform independent and facilitates portability.
2. Garbage Collector that protects from Memory Leaks.
3. Only usage of references and not pointer arithmetic and hence protects the application from memory issues like dangling pointers, memory leaks etc.
4. Support for OOPs that makes application development and maintenance easy.
5. Facilitates library development through use of interface / abstract classes.
6. Facilitates creation of scalable applications.
7. Huge repository of libraries and pool of people with java skill.

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

_{Like Discuss Correct / Improve benefits of java advantages of java basic frequent}

Q1249. String processing in Java

Core Java

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

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

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1250. Explain method overridding.

Core Java

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

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

_{Like Discuss Correct / Improve overridding polymorphism Asked in 1 Companies}

Q1251. How to swap two numbers without using a third variable?

Core Java

Ans. int a = 10;
int b = 20;

b = b + a; // now b is sum of both the numbers
a = b - a; // b - a = (b + a) - a = b (a is swapped)
b = b - a; // (b + a) - b = a (b is swapped)

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

_{Like Discuss Correct / Improve}

Q1252. What's the difference between an array and Vector?

Core Java

Ans. An array groups data of same primitive type and is static in nature while vectors are dynamic in nature and can hold data of different data types.

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

_{Like Discuss Correct / Improve}

Q1253. Can main() method in Java can return any data?

Core Java

Ans. In java, main() method can't return any data and hence, it's always declared with a void return type.

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

_{Like Discuss Correct / Improve}

Q1254. What is the difference between double and float variables in Java?

Core Java

Ans. In java, float takes 4 bytes in memory while Double takes 8 bytes in memory. Float is single precision floating point decimal number while Double is double precision decimal number.

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

_{Like Discuss Correct / Improve}

Q1255. What are Loops in Java? What are three types of loops?

Core Java

Ans. Looping is used in programming to execute a statement or a block of statement repeatedly. There are three types of loops in Java:
1) For Loops
For loops are used in java to execute statements repeatedly for a given number of times. For loops are used when number of times to execute the statements is known to programmer.
2) While Loops
While loop is used when certain statements need to be executed repeatedly until a condition is fulfilled. In while loops, condition is checked first before execution of statements.
3) Do While Loops
Do While Loop is same as While loop with only difference that condition is checked after execution of block of statements. Hence in case of do while loop, statements are executed at least once.

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

_{Like Discuss Correct / Improve}

Q1256. What are the different ways of creating threads in java?

Core Java

Ans. There are two ways to create the threads in java
a) By extending java.lang.Thread class.
b) By implementing java.lang.Runnable interface.

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

_{Like Discuss Correct / Improve}

Q1257. What are the differences between static and non-static methods?

Core Java

Ans. Static method is common to all instances of a class. Static methods are stored in the class memory. Whereas non-static methods are stored in the object memory. Each instance of a class will have their own copy of non-static methods.

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

_{Like Discuss Correct / Improve}

Q1258. What do you mean by inheritance in java?

Core Java

Ans. Inheritance is one of the key principle of object oriented programming. Through inheritance, one class can inherit the properties of another class. The class from which properties are inherited is called super class and the class to which properties are inherited is called sub class.

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

_{Like Discuss Correct / Improve}

Q1259. What are the fundamental principles of object oriented programming? / What are the OOPs concepts?

Core Java

Ans. a) Inheritance
b) Abstraction
c) Polymorphism
d) Encapsulation

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

_{Like Discuss Correct / Improve}

Q1260. What are the main features of Java?

Core Java

Ans. a) Object Oriented
b) Simple
c) Platform Independent
d) Secured
e) Robust
f) Portable
g) Multithreaded
h) Distributed

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

_{Like Discuss Correct / Improve}

Search Interview Questions

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