Core Java Tricky Interview Questions
Demystifying Complex Java Interview Questions
Core Java Tricky Interview Questions are specifically designed to test a candidate's understanding of the fundamental concepts and tricky scenarios in Java programming. These questions often require critical thinking and in-depth knowledge of Java concepts such as inheritance, polymorphism, multithreading, exception handling, and data structures. They may also include scenarios where the candidate needs to identify and fix errors in code, discuss the advantages and disadvantages of different approaches, or explain the intricacies of core Java features. These questions not only evaluate a candidate's technical skills but also their problem-solving abilities and ability to think on their feet. It is important for candidates to fully understand core Java to ace these tricky interview questions.
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1 - What is the difference between a deep copy and a shallow copy in Java?
Deep copy creates a separate copy of an object with its own memory space, whereas shallow copy creates a copy that shares the same memory space as the original object. This means that changes made to the shallow copy will also affect the original object, while changes to the deep copy will not.
2) Can we have multiple inheritances in Java?
No, Java does not support multiple inheritances. This means that a class can only inherit from one superclass at a time. However, a class can implement multiple interfaces, which provides a similar functionality.
3) What is the use of the “static” keyword in Java?
The “static” keyword is used to declare a variable or method that belongs to the class itself rather than an instance of the class. This means that the variable or method can be accessed without creating an instance of the class.
4) Can you explain the difference between an abstract class and an interface?
An abstract class is a class that cannot be instantiated and can contain both concrete and abstract methods. On the other hand, an interface is a collection of abstract methods that must be implemented by the classes that implement it. Additionally, a class can only extend one abstract class, but can implement multiple interfaces.
5) How does garbage collection work in Java?
Garbage collection is a process in Java where the JVM automatically deallocates memory that is no longer in use by the program. This is done by marking objects as eligible for deletion, and then deleting them when the system deems it necessary.
6) Can we override the “main” method in Java?
Yes, we can override the “main” method in Java, but it will not be executed as the entry point for the program. The JVM will always look for a “public static void main(String[] args)” method to start the program.
7) What is the purpose of the try-catch-finally block?
The try-catch-finally block is used for exception handling in Java. The code inside the “try” block is executed, and if any exceptions occur, they are caught by the “catch” block. The “finally” block is used to execute code that must be executed, regardless of whether an exception is caught or not.
8) What are the differences between String, StringBuilder and StringBuffer?
String is an immutable class, meaning it cannot be modified once it is created. StringBuilder and StringBuffer are mutable classes and can be modified. The main difference between StringBuilder and StringBuffer is that StringBuilder is not thread-safe, while StringBuffer is. This means that StringBuffer is slower but safer in a multi-threaded environment.
9) How do you handle errors and exceptions in Java?
In Java, we use the try-catch-finally block to handle errors and exceptions. The “try” block contains code that may throw an exception, which is caught by the “catch” block. The “finally” block is used to execute code that must be executed regardless of whether an exception is thrown or not.
10) What is the difference between the “==” operator and the “equals()” method in Java?
The “==” operator compares the memory addresses of two objects, while the “equals()” method compares the actual values of the objects. This means that two objects can have the same values but different memory addresses, making them not equal with the “==” operator, but equal with the “equals()” method.
11) Can you explain the concept of thread-safety in Java?
A thread-safe code is one that can be accessed concurrently by multiple threads without causing any issues. This means that the code is designed to handle concurrent access and avoid any potential conflicts or race conditions.
12) What is the difference between a String and a StringBuilder in terms of memory usage?
String objects are immutable, meaning that a new object is created every time a modification is made. This can result in a large number of objects in memory, leading to decreased performance. StringBuilder, on the other hand, allows for in-place modifications without creating a new object, resulting in more efficient memory usage.
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13) How does the “final” keyword work in Java?
The “final” keyword can be used to declare a variable, method, or class. When applied to a variable, the value cannot be changed once it has been initialized. When applied to a method, it cannot be overridden in a subclass. And when applied to a class, it cannot be extended.
14) Can you explain the difference between a static and a non-static method?
Static methods are associated with a class and can be accessed without creating an instance of the class. Non-static methods are associated with objects and can only be accessed through an instance of the class.
15) What is the purpose of the “this” keyword in Java?
The “this” keyword is used to refer to the current object in a class. It can be used to access class variables and methods, or to pass the current object as a parameter to another method. This is useful when dealing with variables or methods with the same name in different scopes.
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