Unit 2.2: Boolean Expressions

Relational Operators

Relational operators compare two values and evaluate to a boolean result (true or false).

Comparison Logic

Relational operators allow the computer to ask questions about data. The result is always a boolean value, which can be stored in a variable or used directly in a conditional statement.

Operator	Meaning	Example
`==`	Equal to	`5 == 5` is `true`
`!=`	Not equal to	`5 != 3` is `true`
`<`	Less than	`2 < 10` is `true`
`>`	Greater than	`10 > 2` is `true`
`<=`	Less than or equal to	`5 <= 5` is `true`
`>=`	Greater than or equal to	`3 >= 5` is `false`

Comparing Values

Primitive Types: Relational operators compare the actual values (e.g., 3 == 3).
Reference Types: Relational operators (==, !=) compare the memory addresses (references), not the content of the objects. To compare content, use .equals().

Identity vs. Equality

Identity (==): Checks if two variables point to the exact same location in memory.
Equality (.equals()): Checks if two different objects contain the same data.

Examples

Using Relational Operators

Task: Comparing primitives and object references.

public class BooleanExample {
    public static void main(String[] args) {
        int age = 16;
        double height = 5.9;
        
        // Comparing primitives
        boolean canDrive = age >= 16; // true
        boolean isTall = height > 6.0; // false
        
        System.out.println("Can drive? " + canDrive);
        System.out.println("Is tall? " + isTall);
        
        // Comparing references (Addresses)
        String s1 = new String("Hi");
        String s2 = new String("Hi");
        
        // This is false because they are different objects in memory
        boolean sameObject = (s1 == s2); 
        System.out.println("Same object reference? " + sameObject);

        // This is true because they have the same characters
        boolean sameContent = s1.equals(s2);
        System.out.println("Same content? " + sameContent);
    }
}