Constructors: Default, Parameterized, and Constructor Chaining (this())

Intermediate13 min read•Updated: 2026-10-22

🏗️ Constructors and Constructor Chaining (this())

Introduction

A constructor is a special method invoked automatically upon object creation to establish initial state. Java supports constructor overloading and constructor chaining via the this() call.

🔗 Constructor Chaining with `this()`

Constructor chaining eliminates redundant code by allowing one constructor to delegate to another overloaded constructor in the same class:

Rule: this() must be the very first statement in the constructor!

1public class CourseBatch {
  private String courseCode;
  private String batchName;
  private int maxStudents;
  private boolean isEveningBatch;
6 
  // 1. Fully Parameterized Master Constructor
  public CourseBatch(String code, String name, int capacity, boolean isEvening) {
      this.courseCode = code;
      this.batchName = name;
      this.maxStudents = capacity;
      this.isEveningBatch = isEvening;
  }
14 
  // 2. Overloaded Constructor: Defaults to Morning batch
  public CourseBatch(String code, String name, int capacity) {
      this(code, name, capacity, false); // Delegates to master constructor!
  }
19 
  // 3. Default Constructor: Defaults to standard batch size 30
  public CourseBatch() {
      this("JAVA-101", "Foundation Java Track", 30, false);
  }
24 
  public void display() {
      System.out.printf("[%s] %s | Max: %d | Evening: %b%n", 
          courseCode, batchName, maxStudents, isEveningBatch);
  }
29 
  public static void main(String[] args) {
      CourseBatch b1 = new CourseBatch();
      CourseBatch b2 = new CourseBatch("CPP-201", "Modern C++ Core", 45);
      CourseBatch b3 = new CourseBatch("FS-301", "Full Stack Java", 60, true);
34 
      b1.display();
      b2.display();
      b3.display();
  }
39}

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Instance Variables vs Static Variables & Static Methods	Encapsulation: Access Modifiers (private, default, protected, public) and Getters/Setters

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🔗 Constructor Chaining with this()

Constructor chaining eliminates redundant code by allowing one constructor to delegate to another overloaded constructor in the same class:

Rule: this() must be the very first statement in the constructor!

1public class CourseBatch {
  private String courseCode;
  private String batchName;
  private int maxStudents;
  private boolean isEveningBatch;
6 
  // 1. Fully Parameterized Master Constructor
  public CourseBatch(String code, String name, int capacity, boolean isEvening) {
      this.courseCode = code;
      this.batchName = name;
      this.maxStudents = capacity;
      this.isEveningBatch = isEvening;
  }
14 
  // 2. Overloaded Constructor: Defaults to Morning batch
  public CourseBatch(String code, String name, int capacity) {
      this(code, name, capacity, false); // Delegates to master constructor!
  }
19 
  // 3. Default Constructor: Defaults to standard batch size 30
  public CourseBatch() {
      this("JAVA-101", "Foundation Java Track", 30, false);
  }
24 
  public void display() {
      System.out.printf("[%s] %s | Max: %d | Evening: %b%n", 
          courseCode, batchName, maxStudents, isEveningBatch);
  }
29 
  public static void main(String[] args) {
      CourseBatch b1 = new CourseBatch();
      CourseBatch b2 = new CourseBatch("CPP-201", "Modern C++ Core", 45);
      CourseBatch b3 = new CourseBatch("FS-301", "Full Stack Java", 60, true);
34 
      b1.display();
      b2.display();
      b3.display();
  }
39}

Previous Lesson

Next Lesson

Instance Variables vs Static Variables & Static Methods

Encapsulation: Access Modifiers (private, default, protected, public) and Getters/Setters

🏗️ Constructors and Constructor Chaining (this())

Introduction

🔗 Constructor Chaining with this()

Encapsulation: Access Modifiers (private, default, protected, public) and Getters/Setters

Related Lessons

Practice Quiz

Loading Page Content...

🏗️ Constructors and Constructor Chaining (this())

Introduction

🔗 Constructor Chaining with this()

Encapsulation: Access Modifiers (private, default, protected, public) and Getters/Setters

Related Lessons

Practice Quiz

🔗 Constructor Chaining with `this()`

🔗 Constructor Chaining with `this()`