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

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Q1611. What is a comparator ?

Ans. Java Comparator compares two Java objects in a “compare(Object 01, Object 02)” format. Using configurable methods, Java Comparator can compare objects to return an integer based on a positive, equal or negative comparison

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Q1612. How to make a collection thread safe?

Core Java

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Q1613. What is string pool and what is the use of intern() function ?

Core Java

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

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Q1614. What is Defer Parsing JavaScript ?

JavaScript

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Q1615. 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.

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Q1616. Hash map using/without using Java 8

Core Java

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Q1617. Can we assign the reference to this variable ?

Core Java

Ans. No

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Q1618. What are different types of Polymorphism in Java ?

Core Java

Ans. run time polymorphism
compile time polymorphism

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Q1619. Is String mutable or immutable in Java ?

Core Java

Ans. String is Immutable because of String Constant Pool.

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Q1620. Explain Collections in Java

Core Java

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Q1621. 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.

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Q1622. Write a Program to draw a fish ?

Core Java

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Q1623. What is the difference between inheritance in PHP vs. Javascript?

JavaScript

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Q1624. Write a method to track every click on a page.

JavaScript

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Q1625. Have you had to work with memory leak problems in javascript ?

JavaScript

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Q1626. prototypal inheritance in Javascript

JavaScript

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Q1627. 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 )

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Q1628. 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;
}

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Q1629. Write a unit test case using java 8.

JUnit

Ans. public List convertAllToUpperCase(List words) {
return words.stream().map(String::toUpperCase).collect(Collectors.toList());
}

@Test
public void testAllToUpperCase() {
List expected = Arrays.asList("JAVA8", "STREAMS");
List result = convertAllToUpperCase(Arrays.asList("java8", "streams"));
assertEquals(expected, result);
}

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Q1630. What are the advantages and disadvantages of Lambda Expression ?

Core Java

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Q1631. 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.

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Q1632. 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.

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Q1633. 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.

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Q1634. Difference between Let and Var in Javascript ?

JavaScript

Ans. Var scopes the variable to the nearest function whereas Let scopes the variable to nearest block.

For example -

function printNumbers() {
for(var i = 1; i < 3: i++){
console.log(i);
}

console.log(i); // works fine and will print 3 as i has a function scope and not local loop scope
}

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Q1635. What are benefits of strongly typing variables ?

JavaScript

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Q1636. How is the declaration of enum in Typescript differ from Javascript ?

TypeScript

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Q1637. Interface vs Abstraction

Core Java

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Q1638. Explain Servlet config

Java EE

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Q1639. How Object-Oriented Programming is implemented in JavaScript? How they differ from other languages?

Javascript

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Q1640. How is cohesion achieved in JavaScript ?

JavaScript

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