Java: Check whether a number is a Duck Number or not

Last update on March 11 2025 11:10:09 (UTC/GMT +8 hours)

Check Duck Number

Write a Java program to check whether a number is a Duck Number or not.

Note: A Duck number is a number which has zeroes present in it, but there should be no zero present in the beginning of the number. For example 3210, 7056, 8430709 are all duck numbers whereas 08237, 04309 are not.

Test Data
Input a number : 3210

Pictorial Presentation:

Sample Solution:

Java Code:

import java.util.Scanner;

public class Example15  {

    public static void main(String args[])
       {
        Scanner sc = new Scanner(System.in);
        System.out.print("Input a number : ");
        String nstr = sc.nextLine();
 
        int l = nstr.length();  
        int ctr = 0;  
        char chr;
 
        for(int i=1;i<l;i++)
        {
            chr = nstr.charAt(i); 
            if(chr=='0')
                ctr++;
        }
 
        char f = nstr.charAt(0); 
 
        if(ctr>0 && f!='0')
            System.out.println("Duck number");
        else
            System.out.println("Not a duck number");
    }
}

Sample Output:

Input a number : 3210                                                                                         
Duck number

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to check if a number qualifies as a duck number by ensuring it has zeros but does not start with zero.
• Write a Java program to validate duck numbers using regular expressions to reject numbers with leading zeros.
• Write a Java program to generate a list of duck numbers from a given array of integers.
• Write a Java program to compare a number with its trimmed version to determine if it is a duck number.

Java Code Editor:

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