Getter and setter methods in Java - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of getter and setter usage

What is the output of this Java program that uses getter and setter methods?

Java

public class Person {
    private String name;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public static void main(String[] args) {
        Person p = new Person();
        p.setName("Alice");
        System.out.println(p.getName());
    }
}

A Alice

B null

C Compilation error

D Runtime error

💡 Hint

Look at what value is assigned using the setter before printing with the getter.

The setter method sets the private field 'name' to "Alice". The getter returns this value, so the output is "Alice".

❓ Predict Output

intermediate

Value of private field after setter call

What is the value of the private field 'age' after running this code?

Java

public class Animal {
    private int age;
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        if(age > 0) {
            this.age = age;
        }
    }
    public static void main(String[] args) {
        Animal a = new Animal();
        a.setAge(-5);
        System.out.println(a.getAge());
    }
}

A Compilation error

B 0

C Runtime error

D -5

💡 Hint

Check the condition inside the setter before assigning the value.

The setter only assigns age if the value is greater than 0. Since -5 is not, age remains at default 0.

🔧 Debug

advanced

Identify the error in setter method

What error will this code cause when compiled or run?

Java

public class Car {
    private String model;
    public void setModel(String model) {
        model = model;
    }
    public String getModel() {
        return model;
    }
    public static void main(String[] args) {
        Car c = new Car();
        c.setModel("Tesla");
        System.out.println(c.getModel());
    }
}

A Compilation error due to variable shadowing

B Output is Tesla

C Output is null

D Runtime NullPointerException

💡 Hint

Check if the setter actually changes the private field or just the parameter.

The setter assigns the parameter to itself, not to the field. So the field remains null and output is null.

📝 Syntax

advanced

Syntax error in getter method

Which option shows the correct syntax for a getter method for a private int field 'score'?

A public int getScore() { return score; }

B public int getScore() return score; }

C public int getScore() { score; }

D public int getScore() { return; }

💡 Hint

A getter must return the field value inside braces with a return statement.

Option A correctly defines a method returning the field value. Others have syntax errors or missing return.

🚀 Application

expert

Effect of setter on immutable field

Given this class, what happens when trying to set the 'id' field using the setter?

Java

public class User {
    private final int id;
    public User(int id) {
        this.id = id;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
}

A Setter is ignored silently

B Setter changes the id successfully

C Runtime error when calling setId

D Compilation error because 'id' is final and cannot be assigned in setter

💡 Hint

Final fields cannot be reassigned after initialization.

The setter tries to assign a final field which causes a compilation error.