What is the difference between a default constructor and a parameterized constructor?

Expert Posts
,
1

1. Default Constructor

  • Definition: A default constructor is a no-argument constructor that is automatically provided by the Java compiler if no other constructors are explicitly defined in a class.
  • Purpose: The default constructor initializes an object with default values. For instance, numeric fields are initialized to 0, boolean fields to false, and reference types (objects) to null.
  • Characteristics:
  • No Parameters: As the name suggests, a default constructor has no parameters.
  • Implicitly Provided: If you don’t define any constructor in your class, the Java compiler automatically provides a default constructor.
  • Basic Initialization: It only performs basic initialization, typically setting member variables to their default values.
  • Example:

java public class Example { // No constructor defined, so Java provides a default constructor }

In the above example, the Java compiler automatically provides a default constructor like this:

java public Example() { // Body is empty, no specific initialization code }

2. Parameterized Constructor

  • Definition: A parameterized constructor is a constructor that takes one or more parameters, allowing the user to initialize an object with specific values at the time of creation.
  • Purpose: The parameterized constructor is used to provide different values to the distinct objects of the same class.
  • Characteristics:
  • Accepts Parameters: Unlike the default constructor, a parameterized constructor accepts one or more parameters that can be used to initialize the object’s attributes.
  • Explicitly Defined: It must be explicitly defined by the programmer if there’s a need to initialize the object with specific values.
  • Customized Initialization: Allows for customized initialization of an object depending on the parameters passed.
  • Example:

```java

public class Example {

int number;

String text;

  // Parameterized constructor
  public Example(int num, String txt) {
      this.number = num;
      this.text = txt;
  }

}

```

In this example, the Example class has a parameterized constructor that initializes the number and text attributes with the values provided during object creation.

Key Differences

\| Feature \| Default Constructor \| Parameterized Constructor \|

\|---------------------------\|------------------------------------------------------\|----------------------------------------------------------\|

\| Definition \| A constructor with no parameters \| A constructor that accepts parameters \|

\| Implicit/Explicit \| Implicitly provided by the compiler if none is defined \| Must be explicitly defined by the programmer \|

\| Parameters \| No parameters \| One or more parameters \|

\| Purpose \| Initializes object with default values \| Initializes object with specific values provided by the user \|

\| Usage \| When simple initialization is needed \| When objects need to be initialized with specific values \|

Summary

  • A default constructor is automatically created by the Java compiler if no other constructors are defined and initializes the object with default values.
  • A parameterized constructor is explicitly defined by the programmer and allows for customized initialization of an object by accepting parameters.