How to Invoke One Constructor from Another in Java

What is the method to call one constructor from another constructor in Java?

public class Example {
    private int value;

    // Primary constructor
    public Example(int value) {
        this.value = value;
    }

    // Secondary constructor
    public Example() {
        this(10); // Call primary constructor with a value of 10
    }
}

In Java, you can call one constructor from another constructor within the same class using the 'this' keyword. This can help to reduce code duplication and improve maintainability.

public class Vehicle {
    private String type;

    // Constructor with a string parameter
    public Vehicle(String type) {
        this.type = type;
    }

    // Default constructor that calls the first constructor
    public Vehicle() {
        this("Car"); // Default parameter type is 'Car'
    }

    public String getType() {
        return type;
    }
}

Causes

• Code complexity when multiple constructors perform similar initialization tasks.
• Inconsistencies in initializing class attributes.

Solutions

• Use 'this()' to invoke another constructor within the same class.
• Ensure that the constructor you are invoking has the correct parameter types.
• Avoid circular calls between constructors.

Mistake: Forgetting to use 'this()' when trying to call another constructor.

Solution: Always use 'this()' to reference another constructor.

Mistake: Creating circular constructor calls, which will lead to a compile-time error.

Solution: Ensure that constructors do not call each other indefinitely.