Accenture Interview Questions and Answers

Primary key is a unique identifier for each record in a database table.

• Primary key ensures each record in a table is unique

• It can be a single column or a combination of columns

• Primary key constraints prevent duplicate or null values

Inheritance is a mechanism in Java where a new class inherits properties and behaviors from an existing class.

• Allows for code reusability

• Establishes a parent-child relationship between classes

• Derived class can access methods and fields of the base class

• Can create a hierarchy of classes

Delete removes rows one by one, while truncate removes all rows at once.

• Delete is a DML command, while truncate is a DDL command.

• Delete operation can be rolled back, while truncate operation cannot be rolled back.

• Delete operation fires triggers, while truncate operation does not fire triggers.

• Delete operation is slower as it removes rows one by one, while truncate operation is faster as it removes all rows at once.

Abstraction is the concept of hiding complex implementation details and showing only the necessary features to the outside world.

• Abstraction allows developers to focus on what an object does rather than how it does it

• It helps in reducing complexity and improving maintainability of code

• Example: In Java, abstract classes and interfaces are used to achieve abstraction

HashMap is a data structure in Java that stores key-value pairs and allows fast retrieval of values based on keys.

• HashMap implements the Map interface in Java

• It allows one null key and multiple null values

• Keys in a HashMap must be unique

• Example: HashMap map = new HashMap<>()