Java Fundamentals Assessment

What are the four main data types in Java?

• float, double, char, boolean

• string, object, array, map

• decimal, integer, character, pointer

• byte, short, int, long

What is the difference between int and Integer in Java?

• int can hold null values; Integer cannot.

• Integer is faster than int in performance.

• int is a primitive type; Integer is a wrapper class.

• int is a reference type; Integer is a primitive type.

How do you declare a constant in Java?

• Declare a constant using 'static' keyword.

• Use 'final' keyword to declare a constant, e.g., 'final int MY_CONSTANT = 10;'

• Use 'const' keyword to declare a constant.

• Constants can be declared without any keyword.

What is the purpose of the if-else statement in Java?

• To handle exceptions in the code.

• To control the flow of execution based on conditions.

• To create loops in the program.

• To define variables in Java.

Explain the switch statement and its use cases.

• The switch statement is used for executing different code blocks based on the value of a variable or expression, providing a cleaner alternative to multiple if-else statements.

• The switch statement is a type of loop that repeats code until a condition is met.

• The switch statement can only handle boolean values.

• The switch statement is only used for numerical comparisons.

What is a loop in Java? Name the types of loops available.

• foreach loop

• repeat-until loop

• for loop, while loop, do-while loop

• switch loop

What is the difference between a while loop and a do-while loop?

• A while loop is used for infinite loops, while a do-while loop is for conditional loops.

• The main difference is that a while loop may not execute at all if the condition is false, while a do-while loop always executes at least once.

• Both loops execute the same number of times regardless of the condition.

• A while loop executes at least once, while a do-while loop may not execute at all.

Define a class in Java and its significance in OOP.

• A class in Java is only used for creating interfaces.

• A class in Java is a type of variable that holds data.

• A class in Java is a method for executing code.

• A class in Java is a blueprint for creating objects, encapsulating data and methods, and is significant in OOP for enabling encapsulation, inheritance, and polymorphism.

What is inheritance in Java? Give an example.

• Inheritance is a way to create multiple classes from a single class using the 'implements' keyword.

• Inheritance allows classes to inherit methods from interfaces only.

• Inheritance in Java is achieved through the 'inherits' keyword.

• In Java, inheritance is implemented using the 'extends' keyword. For example: class Animal { void eat() { System.out.println("Eating..."); }} class Dog extends Animal { void bark() { System.out.println("Barking..."); }}

Explain the concept of polymorphism in Java.

• Polymorphism is the ability of a single function or method to operate in different ways based on the object it is acting upon.

• Polymorphism refers to the ability to create multiple instances of a class.

• Polymorphism is the process of converting one data type into another.

• Polymorphism allows multiple classes to inherit from a single class.