Accessor and Mutator Methods in AP CSA

Because instance variables are private, outside code can’t read or modify them directly. Accessor and mutator methods are the controlled gateway — this design principle is called encapsulation.

Accessor Methods (Getters)

Return the value of a private instance variable. Always have a return type that matches the variable. Never void.

public class Student {
    private String name;
    private int grade;

    // Accessor -- returns the value
    public String getName() {
        return name;
    }

    public int getGrade() {
        return grade;
    }
}

Mutator Methods (Setters)

Modify a private instance variable. Almost always void. Can include validation logic.

    // Mutator -- modifies the value
    public void setGrade(int newGrade) {
        if (newGrade >= 0 && newGrade <= 100) {
            grade = newGrade;   // only update if valid
        }
    }