Java Problem Solving Interview Questions
Cracking the Java Coding Interview: Essential Problem Solving Questions
Java Problem Solving Interview Questions are questions designed to assess a candidate's problem solving skills in the context of Java programming language. These questions often require candidates to think critically and analytically in order to identify and solve complex problems using their knowledge of Java syntax, data structures, algorithms, and debugging techniques. They may also test a candidate's ability to troubleshoot and find efficient solutions to common programming problems. Overall, these questions aim to evaluate a candidate's problem solving mindset, coding abilities, and understanding of Java concepts, making them a crucial part of any Java developer interview process.
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1 - What is the difference between an object and a class in Java?
Object is an instance of a class, while class is a template or blueprint from which objects are created. An object has state and behavior, whereas a class defines the behaviors and attributes of objects.
2) What is the difference between a constructor and a method in Java?
A constructor is a special method that is used to initialize objects, whereas a method is a block of code that performs a specific task. A constructor is called when an object is created, whereas a method needs to be explicitly called to execute.
3) What is the difference between an interface and an abstract class in Java?
An interface can only have abstract methods and constants, while an abstract class can also have concrete methods and variables. A class can implement multiple interfaces but can only inherit from one abstract class.
4) What is the difference between a static method and a non-static method in Java?
A static method can be called without creating an instance of the class, while a non-static method can only be called on an object of the class. Static methods are useful for utility functions, whereas non-static methods can access instance variables and are used for object-specific operations.
5) What is the difference between a stack and a queue in Java?
A stack is a data structure that follows Last In First Out (LIFO) principle, whereas a queue follows First In First Out (FIFO) principle. In a stack, elements are added and removed from the top, whereas in a queue, elements are added at the back and removed from the front.
6) How does garbage collection work in Java?
Garbage collection is a process by which the JVM automatically reclaims the memory used by objects that are no longer referenced in the code. The garbage collector runs in the background and identifies objects with no active references and frees the memory associated with them.
7) What is method overloading and method overriding in Java?
Method overloading is having multiple methods with the same name but different parameters, whereas method overriding is redefining a parent class method in a child class with the same signature. Overloading is resolved at compile time, while overriding is resolved at run time.
8) What is the difference between an ArrayList and a LinkedList in Java?
An ArrayList uses a dynamic array to store elements, whereas a LinkedList uses a linked list data structure. Insertion and deletion operations are faster in a LinkedList, whereas retrieval and random access are faster in an ArrayList.
9) How does exception handling work in Java?
Exceptions are used to handle situations that occur during the execution of a program and disrupt the normal flow. When an exception occurs, the program transfers control to the nearest catch block that can handle it. If there is no appropriate catch block, the program terminates with an error.
10) What is the difference between a deep copy and a shallow copy in Java?
A deep copy creates a copy of the object and all its fields, whereas a shallow copy only creates a copy of the object itself without copying its fields. Changes made to the original object after a deep copy are not reflected in the copy, but they are in a shallow copy.
11) What is the difference between HashSet and TreeSet in Java?
A HashSet stores elements in a random order, whereas a TreeSet stores elements in a sorted order. Also, a HashSet allows one null element, whereas a TreeSet does not allow any null elements.
12) How does multithreading work in Java?
Multithreading is a feature that allows a program to execute multiple threads concurrently. Java provides the Thread class and Runnable interface for creating and managing threads. Threads can be started, paused, resumed, and stopped using methods provided by these classes.
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13) What is the difference between String, StringBuilder, and StringBuffer in Java?
String is an immutable class, meaning its value cannot be changed once it is created. StringBuilder and StringBuffer are mutable classes, meaning their values can be modified. StringBuffer is thread-safe, whereas StringBuilder is not.
14) Explain the difference between HashMap and Hashtable in Java?
Both HashMap and Hashtable store data in key-value pairs, but Hashtable is synchronized and thread-safe, whereas HashMap is not. Also, Hashtable does not allow null keys or values, whereas HashMap allows one null key and multiple null values.
15) What is the use of the “this” keyword in Java?
The “this” keyword is used to refer to the current object within a class. It is mainly used to distinguish between local variables and instance variables with the same name, or to pass the current object as a parameter to a method.
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