What Is a Boolean Data Type in Java?


Scott Campbell

When programming in Java, you will often come across the term “boolean data type”. But what exactly is a boolean data type?

In simple terms, a boolean data type represents a binary value, which can be either true or false. It is named after mathematician and logician George Boole, who first introduced the concept of Boolean algebra.

Boolean Variables

In Java, you can declare a boolean variable by using the boolean keyword. For example:

boolean isTrue = true;
boolean isFalse = false;

Here, isTrue and isFalse are boolean variables that store the values true and false respectively. These variables can be used to represent conditions or states in your program.

Boolean Expressions

In addition to boolean variables, you can also create boolean expressions. A boolean expression is an expression that evaluates to either true or false. This is achieved by using logical operators such as ==, <, >, &&, and ||.


  • The double equals sign (==) is used for equality comparison.
  • The less than sign (<) and greater than sign (>) are used for comparison.
  • The double ampersand (&&) represents the logical AND operator.
  • The double pipe (||) represents the logical OR operator.

To better understand boolean expressions, consider the following examples:

int x = 5;
int y = 10;

boolean isEqual = (x == y);         // false
boolean isGreater = (x > y);        // false
boolean isLessThanOrEqual = (x <= y);// true
boolean isBothTrue = (isEqual && isGreater);        // false
boolean isEitherTrue = (isEqual || isGreater);      // false

In this example, isEqual represents the equality comparison between x and y, which evaluates to false since 5 is not equal to 10. Similarly, isGreater represents the comparison of whether x is greater than y, which also evaluates to false.


The result of a boolean expression can be assigned to a boolean variable, as shown in the last two lines of code.

Boolean Control Structures

A common use of boolean data types in Java involves control structures such as if-statements and while-loops. These control structures execute different blocks of code based on the evaluation of a boolean expression.

int number = 7;

if (number % 2 == 0) {
    System.out.println("The number is even.");
} else {
    System.println("The number is odd.");

In this example, we use an if-statement to determine whether a given number is even or odd. The condition inside the parentheses (number % 2 == 0) checks if the remainder of dividing the number by 2 equals zero. If it does, the statement inside the curly braces will be executed; otherwise, the statement inside the else block will be executed.


The if-statement is just one example of a control structure that relies on boolean expressions. There are many other control structures, such as while-loops and for-loops, that utilize boolean expressions to control the flow of execution.


In conclusion, a boolean data type in Java represents a binary value that can be either true or false. It is commonly used to store conditions and evaluate logical expressions. By understanding the concept of boolean data types and how they are used in Java, you can enhance your programming skills and create more robust applications.

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