Variable declaration and initialization in Java - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a variable declaration in Java?

A variable declaration tells the computer to create a space in memory to store a value of a specific type, like int or String.

beginner

What does variable initialization mean?

Initialization means giving a variable its first value when you create it, so it’s ready to use.

beginner

How do you declare and initialize an integer variable named age with the value 25?

You write: int age = 25; This creates the variable and sets its value to 25.

intermediate

Can you declare a variable without initializing it? What happens if you try to use it?

Yes, you can declare a variable without giving it a value. But if you try to use it before setting a value, Java will give an error.

beginner

What is the difference between int x; and int x = 0;?

int x; declares the variable but does not set a value. int x = 0; declares and sets the value to zero.

What does the following code do? <br>double price = 19.99;

A Creates a method named price

B Declares a variable named price and sets it to 19.99

C Declares a variable named price without a value

D Declares a variable named price and sets it to 1999

The code declares a double variable called price and initializes it with 19.99.

Which of these is a valid variable declaration and initialization in Java?

A int number = 10;

B number int = 10;

C int = 10 number;

D int number 10;

Option A correctly declares an int variable named number and initializes it with 10.

What happens if you try to use a variable before initializing it?

A The variable will store null

B Java will assign a default value automatically

C The program will run fine

D Java will give a compile-time error

Java requires variables to be initialized before use, otherwise it gives a compile-time error.

Which keyword is used to declare a variable in Java?

A declare

B int

C No keyword, just the type

D var

In Java, you declare a variable by specifying its type followed by its name, no special keyword like 'declare' is used.

What is the correct way to declare a String variable named name and set it to "Alice"?

A String name = "Alice";

B string name = 'Alice';

C String name = Alice;

D String name := "Alice";

Option A correctly declares a String variable and initializes it with "Alice" using double quotes.

Explain in your own words what variable declaration and initialization mean in Java.

Think about how you tell the computer to remember a value.

Write an example of declaring and initializing a variable for storing a person's height in centimeters.

Use a type that can hold decimal values if needed.