Booleans in Java explained

Getting Started

Diving into the world of programming, you'll inevitably encounter the concept of the boolean data type and its role in the Java universe.

To give you a better comprehension, we'll look into the intricacies but mostly focus on its function as a primitive data type. We'll also include some practical, clear examples to illustrate its usefulness.

Learn about Java Data Types in our beginner's guide

What is a Boolean Data Type?

So, the boolean data type signifies values, with only two possible outcomes: true or false. It plays an essential part in helping us evaluate conditions and direct the program's flow.

Java designates the boolean keyword as a primitive data type, exclusively holding either a true or false value. However, you'll typically encounter boolean expressions utilized to return boolean values for conditional testing purposes.

Working with Boolean Values in Java

Let's demonstrate these claims practically. First, we'll declare and initialize a variable with the boolean keyword, then modify its value and display the results using print statements.

// Declare and initialize the isRaining variable
boolean isRaining = true;

// Print the initial value of isRaining
System.out.println("Is it raining? " + isRaining); // Output: Is it raining? true

// Modify the value of isRaining
isRaining = false;

// Print the updated value of isRaining
System.out.println("Is it raining? " + isRaining); // Output: Is it raining? false

As you can see, we seamlessly transition from one value to another, effectively demonstrating how boolean variables can be employed to represent binary conditions in our code.

Boolean Expressions

In Java, we'll be mostly dealing with boolean expressions that don't explicitly use the boolean keyword. Comparison operators are a prime example of that. Moreover, they allow us to evaluate conditions and introduce some rudimentary logic. Let's take a look at some instances where we utilize these operators to create boolean expressions.

int num1 = 42;
int num2 = 7;

System.out.println(num1 > num2); // returns true

We can expand the example by involving other common comparison operators.

int num1 = 6;
int num2 = 12;

System.out.println(num1 < num2); // Output: true, because 6 is less than 12
System.out.println(num1 == num2); // Output: false, because 6 is not equal to 12
System.out.println(num1 != num2); // Output: true, because 6 is not equal to 12

As you may have noticed, we didn't explicitly declare boolean variables.

Note: Java has several different types of operators, which we'll explore further in a separate article.

Boolean Expressions with Conditional Statements

Moving forward, we can extend the utility of boolean expressions, and showcase their power in combination with conditional statements. Consider a scenario where we're designing a program to calculate the average of three test scores and determine whether the student passed or failed based on their average score.

class Main {
    public static void main(String[] args) {
        double score1 = 85.5;
        double score2 = 90.0;
        double score3 = 75.5;
        double average = (score1 + score2 + score3) / 3.0;

        System.out.println("The student's average score is: " + average);
        if (average >= 60.0) {
            System.out.println("The student passed.");
        } else {
            System.out.println("The student failed.");
        }
    }
}

Initially, we declared three variables related to the score. We then calculate the average score by summing up the individual scores and dividing them by 3. We've opted to use a boolean expression within the if statement to evaluate whether the average score meets or exceeds the passing threshold of 60. If the condition evaluates to true, the program outputs "The student passed."; if not, it displays "The student failed.".

Summary

We focused on the boolean data type and its ability to represent binary values. We also covered how we can declare and initialize boolean variables, used comparison operators to form boolean expressions, and leveraged conditional statements for more elaborate program flow control.

As you apply this concept in your Java programs, be mindful of a few caveats. For instance, while it may be tempting to use integer values like 0 or 1 to represent false or true, it's best to stick with the boolean data type for clarity and consistency. Additionally, pay close attention to operator precedence when crafting complex expressions, as it may impact the evaluation order and ultimately the expression's outcome.

Feel free to check out the additional resources below, and learn more about crucial Java concepts.