Veolia Interview Questions and Answers

No, the 'this' keyword cannot be equal to null.

• The 'this' keyword refers to the current instance of a class.

• It is used to access the members of the current object.

• Since 'this' refers to an object, it cannot be null.

Constructor overriding is not allowed in Java to maintain the integrity of the object creation process.

• Constructor is used to initialize the object state, and allowing overriding can lead to unexpected behavior.

• Inheritance allows the subclass to inherit the superclass constructor, but not override it.

• If a subclass needs to modify the behavior of the superclass constructor, it can use constructor chaining or call a separate method.

• Example: If a subclass overrides the superclas...read more

Normalization is used to eliminate data redundancy and improve data integrity. 3NF ensures that each attribute is dependent on the primary key.

• Normalization helps in organizing data in a structured manner

• It eliminates data redundancy and inconsistencies

• 3NF ensures that each attribute is dependent on the primary key

• For example, a table with columns like Order ID, Product ID, and Customer ID can be normalized to eliminate redundant data

No, static and public cannot be interchanged.

• Static and public are two different keywords in programming.

• Static is used to define a variable or method that belongs to the class itself, rather than an instance of the class.

• Public is an access modifier that allows the variable or method to be accessed from anywhere in the program.

• Interchanging static and public would result in a syntax error.

• For example, in Java, the following code is valid: public static int myVariable = 10;

• Bu...read more

Inheritance is a mechanism in OOP where a new class is derived from an existing class. Overloading is having multiple methods with the same name but different parameters. Overriding is having a method in the subclass with the same name and parameters as in the superclass.

• Inheritance allows for code reuse and promotes code organization.

• Overloading is used to have multiple methods with the same name but different parameters.

• Overriding is used to change the implementation of a m...read more

Types of Constructors

• Default constructor: No arguments, initializes object with default values

• Parameterized constructor: Takes arguments and initializes object with provided values

• Copy constructor: Creates a new object by copying the values of an existing object

• Static constructor: Initializes static members of a class

• Private constructor: Restricts the creation of objects from outside the class

Sort characters in a string based on its frequency.

• Create a dictionary to store character frequency

• Sort the dictionary based on frequency

• Reconstruct the string using the sorted dictionary

Compiler translates entire program at once, while interpreter translates line by line.

• Compiler converts source code into machine code before execution.

• Interpreter converts source code into machine code during execution.

• Compiler produces an executable file that can be run independently.

• Interpreter does not produce an executable file, it executes code directly.

• Compiler optimizations can result in faster execution.

• Interpreter provides easier debugging and error handling.

• Examples...read more