Tutorial Gateway

Java Program to Count Number of Digits in a Number

by

Write a Java Program to Count Number of Digits in a Number using For Loop, While Loop, Functions and Recursion

Java Program to Count Number of Digits in a Number using While Loop

This Java program allows the user to enter any positive integer and then it will divide the given number into individual digits and count those individual digits using Java While Loop.

// Java Program to Count Number of Digits in a Number using While Loop 
package SimplerPrograms;

import java.util.Scanner;

public class NumberofDigitsUsingWhile {
	private static Scanner sc;
	
	public static void main(String[] args) {
		int Number, Count=0;
		sc = new Scanner(System.in);		
		System.out.println("\n Please Enter any Number: ");
		Number = sc.nextInt();
		
		while(Number > 0) {
			Number = Number / 10;
			Count = Count + 1; 
		}
		System.out.format("\n Number of Digits in a Given Number = %d", Count);
	}
}

OUTPUT

Java Program to Count Number of Digits in a Number using While Loop

ANALYSIS

Within the following statements, System.out.println statement will print the statement inside the double Quotes and next we are assigning the user entered value to integer variable (Number)

System.out.println("\n Please Enter any Number: ");
Number = sc.nextInt();

Next line, we used the While loop and the Condition inside the While loop will make sure that, the given number is greater than 0 (Means Positive integer)

while(Number > 0) {
	Number = Number / 10;
	Count = Count + 1; 
}

In this Java Program to Count Number of Digits in a Number example, User Entered value: Number = 1465 and we initialized the Count = 0

First Iteration

Number = Number / 10

Number = 1465 / 10

Number = 146

Count = Count + 1

Count = 0 + 1

Count = 1

Second Iteration

Within the first Iteration the values of both Number and Count has been changed as: Number = 146 and Count = 1

Number = Number / 10

Number = 146 / 10

Number = 14

Count = Count + 1

Count = 1 + 1

Count = 2

Third Iteration

Within the Second Iteration the values of both Number and Count has been changed as: Number = 14 and Count = 2

Number = Number / 10

Number = 14 / 10

Number = 1

Count = Count + 1

Count = 2 + 1

Count = 3

Fourth Iteration

Within the third Iteration the values of both Number and Count has been changed as: Number = 1 and Count = 3

Number = Number / 10

Number = 1 / 10

Number = 0

Count = Count + 1

Count = 3 + 1

Count = 4

Here Number = 0 so, the condition present in the while loop will fail

Last System.out.format statement will print the number of digits present in the given number as output.

System.out.format("\n Number of Digits in a Given Number = %d", Count);

The output of given variable 1465 is 4

Java Program to Count Number of Digits in a Number using For Loop

This Java program allows the user to enter any positive integer and then it will divide the given number into individual digits and then count those individual digits using Java For Loop.

// Java Program to Count Number of Digits in a Number using For Loop 
package SimplerPrograms;

import java.util.Scanner;

public class NumberofDigitsUsingFor {
	private static Scanner sc;
	
	public static void main(String[] args) {
		int Number, Count=0;
		sc = new Scanner(System.in);	
	
		System.out.println("\n Please Enter any Number: ");
		Number = sc.nextInt();
		
		for (Count = 0; Number > 0; Number = Number/10) {
			Count = Count + 1; 
		}
		System.out.format("\n Number of Digits in a Given Number = %d", Count);
	}
}

We just replaced the While loop in the above example with the For loop.

OUTPUT

Java Program to Count Number of Digits in a Number using For Loop

Java Program to Count Number of Digits in a Number Using Functions

In this Java program we are using the same steps that we followed in our second example but we separated the logic and placed in the separate method.

// Java Program to Count Number of Digits in a Number using Functions 
package SimplerPrograms;

import java.util.Scanner;

public class NumberofDigitsUsingFunctions {
	private static Scanner sc;
	private static int Count = 0;
	public static void main(String[] args) {
		int Number;
		sc = new Scanner(System.in);		
		System.out.println("\n Please Enter any Number: ");
		Number = sc.nextInt();

		Count = NumberofDigits(Number);
		System.out.format("\n Number of Digits in a Given Number = %d", Count);
	}
	
	public static int NumberofDigits(int Number) {
		for (Count = 0; Number > 0; Number = Number/10) {
			Count = Count + 1; 
		}
		return Count;
	}
}

OUTPUT

Java Program to Count Number of Digits in a Number using Functions

ANALYSIS

If you observe the following statement, we are calling the NumberOfDigits (Number) method and assigning the return value to integer variable Count.

Count = NumberofDigits(Number);

When the compiler reaches to NumberOfDigits (Number) line in main() program then the compiler will immediately jump to below function:

public static int NumberofDigits(int Number) {

We already explained LOGIC above example.

NOTE: If we create a function with Void then there is no need to return any value but, if we declared a function with any data type (int, float etc) then we have to return something out from the function.

Java Program to Count Number of Digits in a Number Using Recursion

This Java program allows the user to enter any positive integer and then it will divide the given number into individual digits and counting those individual digits using Java Recursion concept. In this example, we are dividing the code using the Object Oriented Programming. To do this, First we will create a class which holds a method to count number of digits in a number recursively.

package SimplerPrograms;

public class NumberofDigits {
	int Count = 0;
	public int DigitsCount(int Number) {
		if(Number > 0) {
			Count = Count + 1; 
			DigitsCount(Number / 10);
		}
		return Count;
	}

}

Within the Main Program to Count Number of Digits in a Number, we will create an instance of the above specified class and call the methods

package SimplerPrograms;

import java.util.Scanner;

public class NumberofDigitsUsingRecursion {
	private static Scanner sc;
	
	public static void main(String[] args) {
		int Number, Count=0;
		sc = new Scanner(System.in);		

		System.out.println("\n Please Enter any Number: ");
		Number = sc.nextInt();
		
		NumberofDigits nd = new NumberofDigits();
		Count = nd.DigitsCount(Number);

		System.out.format("\n Number of Digits in a Given Number = %d", Count);
	}
}

OUTPUT

Java Program to Count Number of Digits in a Number using Recursion

ANALYSIS

NumberOfDigits Class Analysis:

In this Java Program to Count Number of Digits in a Number, First we declared an integer function DigitsCount with one argument. Within the function, we used the If statement to check whether the given number is greater than Zero or Not and if it is True then statements inside the If block will be executed. It means:

  • Count will be incremented by 1 using Count = Count + 1
  • DigitsCount (Number / 10) statement will help to call the function Recursively with updated value. If you miss this statement then, after completing the first line it will terminate.

TIP: If you declare a method with void keyword then we can’t return any value. If you want to return any value then replace void with data type and add return keyword.

Main Class Analysis:

First we created an instance / created an Object of the NumberOfDigits Class

NumberofDigits nd = new NumberofDigits();

Next, we are calling the DigitsCount method.

Count = nd.DigitsCount(Number);

Lastly, System.out.println statement will print the output (987654321 = 9).