Constructor getParameterCount() method in Java with Examples

Last Updated : 29 Oct, 2019

The getParameterCount() method of java.lang.reflect.Constructor class is used to return the number of parameters present on this constructor object. Every constructor contains a number of parameters starting from zero to many. This method is helpful to get those numbers of parameters. Syntax:

public int getParameterCount()

Parameters: This method accepts nothing. Return: This method returns the number of formal parameters for the executable this object represents. Below programs illustrate getParameterCount() method: Program 1:

Java

// Java program to illustrate getParameterCount() method

import java.lang.reflect.Constructor;

public class GFG {

    public static void main(String[] args)
    {
        // create a class object
        Class classObj = String.class;

        // get Constructor object
        // array from class object
        Constructor[] cons = classObj.getConstructors();

        // get count of parameter
        int params = cons[0].getParameterCount();

        // print parameter count
        System.out.println("No of Parameters: " + params);
    }
}

Output:

No of Parameters: 3

Program 2:

Java

// Java program to illustrate getParameterCount() method

import java.lang.reflect.Constructor;
import java.util.ArrayList;

public class GFG {

    public static void main(String[] args)
    {
        // create a class object
        Class classObj = ArrayList.class;

        // get Constructor object
        // array from class object
        Constructor[] cons = classObj.getConstructors();

        for (int i = 0; i < cons.length; i++) {
            // get count of parameter
            int params = cons[i].getParameterCount();

            // print parameter count
            System.out.println(
                cons[i].toGenericString()
                + "-> parameter count = " + params);
        }
    }
}

Output:

public java.util.ArrayList(java.util.Collection)-> parameter count = 1
public java.util.ArrayList()-> parameter count = 0
public java.util.ArrayList(int)-> parameter count = 1

References: https://docs.oracle.com/javase/10/docs/api/java/lang/reflect/Constructor.html#getParameterCount()