POSCO MAHARASHTRA STEEL Interview Questions and Answers

The static keyword in Java is used to create variables and methods that belong to the class rather than instances of the class.

• Static variables are stored in the static memory area, also known as the method area or permanent generation.

• Static variables are shared among all instances of a class.

• Static methods can be called without creating an instance of the class.

• Static variables and methods can be accessed using the class name followed by the dot operator.

• A programmatic situ...read more

Polymorphism is the ability of an object to take on many forms. Runtime polymorphism is achieved through method overriding.

• Polymorphism allows objects of different classes to be treated as objects of a common superclass.

• Static polymorphism is achieved through method overloading.

• Runtime polymorphism is determined at runtime based on the actual type of the object.

• Static polymorphism is determined at compile-time based on the number and types of arguments passed to a method.

• Exam...read more

String is immutable because it ensures data integrity and thread safety. StringBuffer and StringBuilder are mutable alternatives.

• String is immutable, meaning its value cannot be changed once created.

• Immutable strings ensure data integrity and thread safety.

• StringBuffer and StringBuilder are mutable alternatives to String.

• StringBuffer is synchronized and thread-safe, but slower.

• StringBuilder is not synchronized, faster, but not thread-safe.

• Example: String name = "John"; name +...read more

Multiple inheritance is when a class inherits from more than one base class. Multilevel inheritance is when a class inherits from another derived class.

• Multiple inheritance allows a class to inherit attributes and behaviors from multiple parent classes.

• Multilevel inheritance involves a chain of inheritance where a derived class inherits from another derived class.

• In multiple inheritance, conflicts may arise if two base classes have methods with the same name.

• In multilevel inh...read more

The abstract keyword is used in object-oriented programming to declare a class or method as abstract.

• An abstract class cannot be instantiated and can only be used as a base for other classes.

• An abstract method is a method without a body, and it must be implemented by any concrete subclass.

• Abstract classes can have both abstract and non-abstract methods.

• Abstract methods are used to define a common interface that all subclasses must implement.

• The abstract keyword allows for the...read more

The main OOPs concepts are encapsulation, inheritance, and polymorphism.

• Encapsulation: bundling of data and methods into a single unit (class) to hide implementation details.

• Inheritance: ability of a class to inherit properties and methods from another class.

• Polymorphism: ability of objects of different classes to be treated as objects of a common superclass.

Java implements multiple inheritance through interfaces.

• Java does not support multiple inheritance of classes.

• Instead, it allows multiple inheritance of interfaces.

• A class can implement multiple interfaces, inheriting their methods and constants.

• Interfaces provide a way to achieve multiple inheritance without the complexities of class inheritance.

• Example: class A implements Interface1, Interface2 { ... }

The optimized solution to print prime numbers between 1 to n.

• Start with a loop from 2 to n

• For each number, check if it is divisible by any number from 2 to its square root

• If it is not divisible by any number, it is a prime number and can be printed