Parameterized constructor in Java - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a parameterized constructor in Java?

A parameterized constructor is a special method in a class that takes parameters to initialize an object with specific values when it is created.

beginner

How does a parameterized constructor differ from a default constructor?

A default constructor has no parameters and initializes objects with default values, while a parameterized constructor requires arguments to set custom initial values.

beginner

Why use a parameterized constructor?

It allows creating objects with different initial states easily by passing different values when creating each object.

beginner

Example of a parameterized constructor in Java:

class Car {
  String model;
  int year;
  Car(String m, int y) {
    model = m;
    year = y;
  }
}
// Creates a Car object with model and year set

intermediate

What happens if you define a parameterized constructor but no default constructor?

Java does not create a default constructor automatically, so you must define one if you want to create objects without parameters.

What is the main purpose of a parameterized constructor?

A To create multiple objects at once

B To initialize an object with specific values

C To delete an object

D To convert an object to a string

A parameterized constructor initializes an object with values passed as parameters.

What happens if you do not define any constructor in a Java class?

A The program will not compile

B The class cannot be instantiated

C You must always define a constructor

D Java provides a default constructor automatically

If no constructor is defined, Java automatically provides a default constructor with no parameters.

Which of these is a valid parameterized constructor signature?

A Car(String model, int year)

B void Car()

C Car()

D int Car(String model)

A constructor has the same name as the class and no return type.

If a class has only a parameterized constructor, what happens when you try to create an object without arguments?

A Compilation error

B Object is created with default values

C Object is created with null values

D Runtime exception

Without a default constructor, creating an object without arguments causes a compilation error.

How do you call a parameterized constructor when creating an object?

A ClassName()

B ClassName.new()

C new ClassName(arguments)

D new ClassName()

You call a parameterized constructor by passing arguments inside parentheses after new.

Explain what a parameterized constructor is and why it is useful.

Think about how you give specific details when creating something new.

Write a simple Java class with a parameterized constructor and explain how to create an object using it.

Start with a class name and add a constructor that takes inputs.