Java is a computer language that is object-oriented. It's the most popular programming language for Android development. It may also be used to create desktop apps, online apps, and web services. As a result, we've compiled a list of the most critical Java Interview Questions you'll need to answer in order to land your ideal job in the IT business.
1.What distinguishes Java from other programming languages?
ANS:Java is an Object-Oriented Programming Language that has the following characteristics: – High Performance
It is multi-threaded.
Easy to understand
2.Is Pointers Supported in Java?
ANS:To make java more safe, pointers are not supported.
3.In Java, why are static variables used?
ANS:Java uses static methods and variables to keep a single copy of the item across all instances. When a variable is defined as static, all instances of the class share it. Changes to the variable made by one instance are reflected across all instances.
4.What are static methods, static variables, and static blocks?
ANS:Static methods, static variables, and static blocks are all terms that refer to the same thing.
Methods that may be called directly inside a class without the usage of an object are known as static methods.
Variables that are shared by all instances of a class are known as static variables.Static blocks are code blocks that are loaded at the same time as the class.
5.What are the benefits of using static methods?
ANS:When there is no need to instantiate a class, static methods are utilised. A method can be declared static if it is not going to change or be overwritten.
6.What are the benefits of using static variables?
ANS:Static variables are used to save a common state of data that can be changed and accessed by all instances of a class.
7.What are the interfaces?
ANS:An interface is a collection of constants, static methods, abstract methods, and default methods. Methods in an interface do not have a body.
8.In Java, how is abstraction achieved?
ANS:Abstract classes and abstract methods are used in Java to accomplish abstraction.
9.Why are strings immutable in Java?
ANS:Strings in java are frequently used for hashmap keys. Now if someone changes the value of the string it will cause severe discrepancies. Hence strings are made immutable.
10.In Java, what are wrapper classes?
ANS:Wrapper classes are a Java feature that allows you to take basic data types as input and transform them to string objects so you may compare them to other things.
11.Is it possible to inherit Java interfaces?
ANS:In Java, interfaces can be inherited. Java supports hybrid inheritance and hierarchical inheritance via inheritable interfaces.
12.Is it possible to use static methods in a Java interface?
ANS:In Java interfaces, static methods are permitted. They are not required to be implemented because they are default methods.
13.In Java, how does trash collection work?
ANS:There is an automated garbage collection method integrated into Java. Aside from the built-in technique, the system class's gc() can be used to manually initiate garbage collection.
14.Is it possible for a class to have two primary methods?
ANS:Yes, there are two primary approaches. The main method is likewise overloaded as a result of this. However, JVM just calls the regular main function during execution, not the overloaded main method.
15.Is it possible to inherit private variables?
ANS:The availability of private variables is class-specific. Only the methods of the class in which they are contained can access them. As a result, private variables are not inherited by the subclass when the class is inherited.
16.Is it possible to raise the size of an array after it has been declared?
ANS:A java array's size cannot be extended once it has been declared. Java arrays have this restriction.
17.What is the memory size of the array below?
ANS:int a=new int; Each int block is 4 bytes long, and the array has 10 of them. As a result, the array occupies 40 bytes in memory.
18.Java supports how many different data types?
ANS:The primitive data types supported by Java include byte, short, int, long, float, double, char, and boolean.
19.In Java, how do you find the ASCII value of a character?
ANS:In Java, int c=char('A') returns the ASCII value of A.
20.How can I obtain a string from the terminal as user input?
ANS:First, we must create an input reader class. There are a number of choices, including BufferedReader and InputStreamReader Scanner.
The class's related functionality can then be utilised. The Scanner class's nextLine() method is one of the most commonly utilised.
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