Fidelity International Interview Questions and Answers

Overloading with different return type is not allowed in Java.

• Overloading is based on method signature, not return type

• Methods with same name and different return type will result in compile-time error

• Example: int add(int a, int b) and double add(int a, int b) is not allowed

Use a set to remove duplicates from a string array.

• Create a set to store unique strings.

• Iterate through the array and add each string to the set.

• Convert the set back to an array to get the unique strings.

Authentication in web API is achieved by using tokens or API keys to verify the identity of users.

• Use tokens (such as JWT) to authenticate users

• Implement OAuth for secure authentication

• Utilize API keys for authentication purposes

Sealed virtual static new keywords are used in C# to control inheritance and method hiding.

• Sealed keyword prevents a class from being inherited.

• Virtual keyword allows a method to be overridden in derived classes.

• Static keyword makes a member of a class accessible without creating an instance of the class.

• New keyword hides a method from the base class in the derived class.

Interface defines a contract for classes to implement, while abstract class can have both abstract and concrete methods.

• Interfaces can only have abstract methods and constants, while abstract classes can have both abstract and concrete methods.

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

• Interfaces are used to achieve multiple inheritance in Java, while abstract classes are used to provide a common base for subclasses.

Diff string string builder compares two strings and returns the differences.

• Use a loop to iterate through each character of the strings

• Compare characters at the same index in both strings

• Build a new string with the differing characters

Arrays are fixed in size, while ArrayLists can dynamically resize.

• Arrays have a fixed size determined at initialization, while ArrayLists can dynamically resize.

• Arrays are faster for accessing elements, while ArrayLists are better for adding or removing elements.

• Arrays use [] syntax for accessing elements, while ArrayLists use get() and set() methods.

• Arrays can only store primitive types, while ArrayLists can store objects.

Diff method compares values of two objects while equal method compares references of two objects.

• Diff method compares values of two objects, while equal method compares references.

• Diff method is used to check if two objects are different, while equal method is used to check if two objects are the same.

• Example: obj1.diff(obj2) vs obj1.equal(obj2)