Parameterized Constructor in Java

A parameterized constructor is a constructor that accepts arguments, allowing you to initialize an object's fields with specific values at the time of its creation.

Syntax

class ClassName {
    ClassName(parameterType parameterName) {
        // initialization code
    }
}

Example

class Student {
    String name;
    int age;

    Student(String name, int age) {
        this.name = name;
        this.age = age;
    }
}

Student s1 = new Student("Aman", 22);
Student s2 = new Student("Priya", 24);

Key Points

• Parameterized constructors let each object be initialized with different values right at creation
• Once a class defines a parameterized constructor, Java no longer provides a default no-arg constructor automatically
• A class can have multiple parameterized constructors through constructor overloading

Why Use Parameterized Constructors?

• Avoids the need to set every field manually with setters after creating the object
• Makes sure objects are created in a valid, fully-initialized state
• Improves readability, since the values passed during creation are visible at a glance