Essential Java Basics Quiz Quiz

Assess your foundational understanding of Java programming concepts relevant to backend development. Ideal for beginners aiming to strengthen their Java fundamentals.

1. Java Data Types

   Which keyword is used to declare a variable that holds whole numbers in Java, such as 10 or -5?

   1. char
   2. bool
   3. float
   4. int

   Explanation: The 'int' keyword declares a variable for whole numbers. 'bool' is not a valid keyword in Java; Java uses 'boolean' for true/false values. 'char' is meant for single characters. 'float' is for decimal numbers, not integers.

2. Java Entry Point

   What is the correct signature for the main method that serves as the starting point of a Java application?

   1. static void main(String args)
   2. public static void main(String[] args)
   3. public void main()
   4. void public main(String args[])

   Explanation: 'public static void main(String[] args)' is the required entry point for Java applications. The others either have incorrect order, missing 'static', wrong parameter types, or lack required array syntax.

3. Java Comments

   How do you write a single-line comment in Java to describe your code?

   1. # This is a comment
   2. // This is a comment
   3. -- This is a comment
   4. <!-- This is a comment -->

   Explanation: // begins a single-line comment in Java. '#' is used in languages like Python, '--' is used in SQL, and '<!-- -->' is for HTML comments.

4. Object Creation

   Which code correctly creates a new object from the 'Car' class in Java?

   1. myCar = new Car;
   2. Car myCar = Car();
   3. Car = myCar new();
   4. Car myCar = new Car();

   Explanation: The correct object creation syntax is 'Car myCar = new Car();'. The other options either miss required syntax like 'new', parentheses, or use an invalid order of elements.

5. Variable Naming

   Which of these is a valid variable name in Java?

   1. totalAmount
   2. class
   3. total-amount
   4. 2value

   Explanation: 'totalAmount' is a valid variable name as it starts with a letter and has no forbidden characters. '2value' starts with a digit, which is not allowed. 'class' is a reserved keyword, and 'total-amount' includes a hyphen, which is invalid.