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Java Constructors

Constructors in Java are special methods used to initialize objects. They have the same name as the class and do not have a return type. Constructors are called when an object is created using the new keyword.

1. Default Constructor

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

2. Parameterized Constructor

You can define constructors with parameters to initialize object attributes with specific values.

public class Person {
    String name;
    int age;

    // Parameterized constructor
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }
}

3. Creating Objects with Constructors

Person person = new Person("Alice", 30);
System.out.println(person.name); // Outputs: Alice

4. Constructor Overloading

You can have multiple constructors in a class with different parameters.

public class Rectangle {
    int width;
    int height;

    // No-argument constructor
    public Rectangle() {
        width = 0;
        height = 0;
    }

    // Parameterized constructor
    public Rectangle(int w, int h) {
        width = w;
        height = h;
    }
}

5. The this Keyword

The this keyword refers to the current object. It's used to differentiate between class attributes and parameters with the same name.

Key Takeaways

  • Constructors initialize new objects.
  • They have the same name as the class and no return type.
  • Parameterized constructors allow setting initial values for attributes.
  • Constructor overloading provides flexibility in object creation.
  • The this keyword helps in referencing the current object's attributes.
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