10+ System Trainee Interview Questions and Answers

Yes, static methods can be used in an interface.

• Static methods in an interface can be used to provide utility methods that are not tied to any specific instance of the interface.

• These methods can be called directly on the interface itself, without the need for an instance of a class that implements the interface.

• Static methods in an interface cannot be overridden by implementing classes.

• They can be useful for providing common functionality or helper methods that are related t...read more

Variables in Java are containers that store data values. Their scope determines where they can be accessed.

• Java has three types of variables: local, instance, and static

• Local variables are declared within a method and can only be accessed within that method

• Instance variables are declared within a class but outside of any method and can be accessed by any method within that class

• Static variables are declared with the static keyword and can be accessed by any method within that...read more

Abstract classes are classes that cannot be instantiated and can have both concrete and abstract methods. Interfaces are contracts that define a set of methods that a class must implement.

• Abstract classes can have instance variables, constructors, and non-abstract methods, while interfaces cannot.

• A class can implement multiple interfaces, but it can only inherit from one abstract class.

• Abstract classes provide a way to share code among related classes, while interfaces define...read more

Polymorphism in Java can be achieved through method overriding and method overloading.

• Method overriding allows a subclass to provide a different implementation of a method that is already defined in its superclass.

• Method overloading allows multiple methods with the same name but different parameters to be defined in a class.

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

• Example of method overriding: public class Animal { publi...read more

Program to reverse a string

• Declare a string variable

• Loop through the string from end to start

• Append each character to a new string variable

• Return the new string variable

Polymorphism is the ability of an object to take on multiple forms.

• Polymorphism allows objects of different classes to be treated as if they are of the same class.

• It can be achieved through method overloading or method overriding.

• Example: A parent class Animal can have multiple child classes like Dog, Cat, etc. and all of them can have their own implementation of the same method like makeSound().

• Polymorphism helps in achieving loose coupling and flexibility in code design.

C is a procedural language while Java is an object-oriented language.

• C is compiled while Java is interpreted

• Java has automatic garbage collection while C requires manual memory management

• Java has platform independence while C is platform dependent

• Java has built-in exception handling while C does not

• Java has a larger standard library than C

OOPs is a programming paradigm based on the concept of objects that interact with each other to perform tasks.

• OOPs stands for Object-Oriented Programming

• It involves the use of classes, objects, encapsulation, inheritance, and polymorphism

• Classes are blueprints for creating objects

• Objects are instances of classes

• Encapsulation is the process of hiding data and methods within a class

• Inheritance allows a class to inherit properties and methods from another class

• Polymorphism allow...read more

Oops concepts are fundamental to Java programming and include inheritance, polymorphism, encapsulation, and abstraction.

• Inheritance allows a class to inherit properties and methods from a parent class.

• Polymorphism allows objects to take on multiple forms and behave differently based on their context.

• Encapsulation hides the implementation details of a class from other classes.

• Abstraction allows us to focus on the essential features of an object and ignore the rest.

• Examples inc...read more

Exception handling in Java is a mechanism to handle runtime errors and prevent program termination.

• Java provides try-catch blocks to handle exceptions

• Multiple catch blocks can be used to handle different types of exceptions

• Finally block is used to execute code regardless of whether an exception is thrown or not

• Custom exceptions can be created by extending the Exception class

• Checked exceptions must be handled or declared in the method signature

• Unchecked exceptions do not need ...read more