Accessors

public class Student {
    private String name;
    private int grade;
    private double gpa;
    
    public Student(String name, int grade, double gpa) {
        this.name = name;
        this.grade = grade;
        this.gpa = gpa;
    }
    
    // Accessors — read data
    public String getName() {
        return name;
    }
    
    public int getGrade() {
        return grade;
    }
    
    public double getGpa() {
        return gpa;
    }
}

public class Student {
    private String name;
    private int grade;
    private double gpa;
    
    // ... constructor and getters ...
    
    // Mutators — change data
    public void setName(String name) {
        this.name = name;
    }
    
    public void setGrade(int grade) {
        if (grade >= 9 && grade <= 12) {
            this.grade = grade;
        }
    }
    
    public void setGpa(double gpa) {
        if (gpa >= 0.0 && gpa <= 4.0) {
            this.gpa = gpa;
        }
    }
}

public class BankAccount {
    private double balance;
    
    public void setBalance(double balance) {
        if (balance >= 0) {
            this.balance = balance;   // only set if non-negative
        }
        // otherwise, do nothing — balance stays the same
    }
    
    public void deposit(double amount) {
        if (amount > 0) {
            balance += amount;
        }
    }
    
    public boolean withdraw(double amount) {
        if (amount > 0 && amount <= balance) {
            balance -= amount;
            return true;
        }
        return false;   // withdrawal failed
    }
}

public class Rectangle {
    private double width;
    private double height;
    
    public Rectangle(double width, double height) {
        this.width = width;
        this.height = height;
    }
    
    // Simple accessors
    public double getWidth() { return width; }
    public double getHeight() { return height; }
    
    // Computed accessors — derived from instance variables
    public double getArea() {
        return width * height;
    }
    
    public double getPerimeter() {
        return 2 * (width + height);
    }
    
    public boolean isSquare() {
        return width == height;
    }
}

public class Thermostat {
    private double temperature;
    private boolean isCelsius;
    
    public Thermostat(double temp, boolean celsius) {
        this.temperature = temp;
        this.isCelsius = celsius;
    }
    
    // Accessor
    public double getTemperature() {
        return temperature;
    }
    
    // Computed accessor
    public double getTemperatureF() {
        if (isCelsius) {
            return temperature * 9.0 / 5.0 + 32;
        }
        return temperature;
    }
    
    // Accessor (boolean → use "is" prefix)
    public boolean isCelsius() {
        return isCelsius;
    }
    
    // Mutator
    public void setTemperature(double temp) {
        temperature = temp;
    }
    
    // Mutator — increase temperature
    public void increaseBy(double degrees) {
        if (degrees > 0) {
            temperature += degrees;
        }
    }
    
    // Mutator — switch between C and F
    public void toggleScale() {
        if (isCelsius) {
            temperature = temperature * 9.0 / 5.0 + 32;
        } else {
            temperature = (temperature - 32) * 5.0 / 9.0;
        }
        isCelsius = !isCelsius;
    }
}

Thermostat t = new Thermostat(100, true); // 100°C
t.increaseBy(5);                           // 105°C
System.out.println(t.getTemperatureF());   // 221.0°F
t.toggleScale();                           // now 221.0°F
System.out.println(t.getTemperature());    // 221.0
t.toggleScale();                           // back to 105.0°C