Top 50 Java Programming Interview Questions

They collaborate with teams, solve problems, and ensure code quality for efficient and reliable software development. Finally is a block of code used with “try-catch” in exception handling. Code written in finally block runs despite the fact exception is thrown or not.

Q47: Can we override static methods in Java?

Since an anonymous class has no name, it is not possible to define a constructor for an anonymous class. Anonymous inner classes are accessible only at the point where it is defined. If we have to use any static variable or method from other class, usually we import the class and then use the method/variable with class name. Java’s final keyword can be used with variables to make sure that it can be assigned only once. However the state of the variable can be changed, for example, we can assign a final variable to an object only once but the object variables can change later on.

Write a Java program to check if the two strings are anagrams.

  1. Java provides automatic serialization which requires that the object be marked by implementing the interface.
  2. Java libraries are a collection of precompiled routines that a program can use.
  3. A class contains fields (variables) and methods to describe the behavior of an object.
  4. Well, you really need to know the concept of string pool very deeply to answer this question or similar questions.
  5. The Connection interface maintains a session with the database.

An interface can extend multiple interfaces because they just declare the methods and implementation will be present in the implementing class. So there is no issue of the diamond problem with interfaces. Core Java interview questions help you in preparing for java based interviews. Whether you are a fresher or highly experienced professional, core java plays a vital role in any Java/JEE interview. The constructor can never be declared as final because it is never inherited. Constructors are not ordinary methods; therefore, there is no sense to declare constructors as final.

How do you create text blocks in Java?

By default, the JIT compiler is enabled in Java and is activated whenever a Java method is invoked. The JIT compiler then compiles the bytecode of the invoked method into native machine code, compiling it “just in time” to execute. java interview questions for senior developer Once the method has been compiled, the JVM summons the compiled code of that method directly rather than interpreting it. This is why it is often responsible for the performance optimization of Java applications at the run time.

Can we make the abstract methods static in Java?

Unlike Comparable, Comparator is external to the element type we are comparing. We create several different classes (using Comparator) to compare different members. The Collections class has a second sort() method and accepts a Comparator. To compare its instances, the class itself must implement the java.lang.Comparable interface.

Explain the difference between instance variable and a class variable.

It always executes , whether there is an exception or not. There are only a few situations in which the finally block does not execute, such as VM crash, power failure, software crash, etc. If you don’t want to execute the finally block, you need to call the System.exit() method explicitly in the finally block. Java String pool refers to a collection of Strings which are stored in heap memory.

What do you understand by copy constructor in Java?

Some of the important classes provided by Collection API include ArrayList, HashMap, TreeSet and TreeMap. In order to throw an exception in a block of code manually, throw keyword is used. Then this exception is caught and handled in the catch block. Once an object has been destroyed by garbage collector, it no longer exists on the heap and it can’t be accessed again. Main method is an entry point of Java class and is required for execution of the program however; a class gets compiled successfully even if it doesn’t have a main method. Java provides a default no argument constructor if no explicit constructor is defined in a Java class.

Read important points about abstract classes at java abstract class. Abstract classes are used in java to create a class with some default method implementation for subclasses. An abstract class can have an abstract method without the body and it can have methods with implementation also. To reduce the complexity and simplify the language, multiple inheritance is not supported in java.

It is a programming paradigm based on objects having data and methods defined in the class to which it belongs. Object-oriented paradigm aims to incorporate the advantages of modularity and reusability. Objects are the instances of classes which interacts with one another to design applications and programs.

It is the simplest way of executing the computer code that takes in compilation during the execution of a program rather than before performance. Delete, Next, Exit are the operations performed in the Java program, Main is the predefined method, and Null is the default String type. The request and session scopes are only available in a web-based context.

Contiguous memory locations are usually used for storing actual values in an array but not in ArrayList. The program outputs the index where the element is found or a message indicating that the element was not found in the array. Code challenges are a great way to improve your coding skills. Try these 10 advanced Java code challenges to put your Java programming knowledge to the test. A stack is based on the principle of Last In, First Out (LIFO). A queue is different in that it’s based on the First In, First Out (FIFO) principle.

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