How to Find Length of Integer in Java?

In this section, we will learn the different approaches to find the length of an integer in Java. The length of an integer means the total number of digits present in that integer.

We can find the length of integer by using the following approaches:

Using while loop
Using String
Using Continuous Multiplication
Using Logarithm
Using Recusion

Let's discuss one by one.

Using while loop

We can find the length of an integer using a while loop. Observe the following code.

FileName: IntegerLengthExample.java

public class IntegerLengthExample
{
// method to find the number of digits present in the number n
public int countDig(int n)
{
int count = 0;
while(n != 0)
{
// removing the last digit of the number n
n = n / 10;
// increasing count by 1
count = count + 1;
}
return count;
}
// main method
public static void main(String argvs[])
{
// input array
int arr[] = {78, 9, 2345, 899009, 1, 414, 34, 1000, 2749};
// size of the input arrray
int size = arr.length;
// creating an object of the class IntegerLengthExample
IntegerLengthExample obj = new IntegerLengthExample();
for(int i = 0; i < size; i++)
{
int count = obj.countDig(arr[i]);
System.out.println("The length of the number " + arr[i] + " is " + count);
}
}
}

Output:

The length of the number 78 is 2
The length of the number 9 is 1
The length of the number 2345 is 4
The length of the number 899009 is 6
The length of the number 1 is 1
The length of the number 414 is 3
The length of the number 34 is 2
The length of the number 1000 is 4
The length of the number 2749 is 4

Using String

Another idea can be to convert the number into a string and then compute its size. The size of the string gives the length of the string. The following program depicts the same.

FileName: IntegerLengthExample1.java

public class IntegerLengthExample1
{
// method to find the number of digits present in the number n
public int countDig(int n)
{
// converting the number n to a string
String str = Integer.toString(n);
// computing the size of the string
int size = str.length();
return size;
}
// main method
public static void main(String argvs[])
{
// input array
int arr[] = {78, 9, 2345, 899009, 1, 414, 34, 1000, 2749};
// size of the input arrray
int size = arr.length;
// creating an object of the class IntegerLengthExample1
IntegerLengthExample1 obj = new IntegerLengthExample1();
for(int i = 0; i < size; i++)
{
int count = obj.countDig(arr[i]);
System.out.println("The length of the number " + arr[i] + " is " + count);
}
}
}

Output:

The length of the number 78 is 2
The length of the number 9 is 1
The length of the number 2345 is 4
The length of the number 899009 is 6
The length of the number 1 is 1
The length of the number 414 is 3
The length of the number 34 is 2
The length of the number 1000 is 4
The length of the number 2749 is 4

Using Continuous Multiplication

We can multiply a number 1 by 10 until it becomes greater than the number n. Each time we multiply by 10, we increment a variable count by 1. The final value of the count gives the length of the integer n. Let's understand it with the help of the following program.

FileName: IntegerLengthExample2.java

public class IntegerLengthExample2
{
// method to find the number of digits present in the number n
public int countDig(int n)
{
int temp = 1;
int count = 0;
while(temp <= n)
{
// multiplying temp by 10
temp = temp * 10;
// increasing the value of count by 1
count = count + 1;
}
// count contains the total number of 
// digits present in the number n
return count;
}
// main method
public static void main(String argvs[])
{
// input array
int arr[] = {78, 9, 2345, 899009, 1, 414, 34, 1000, 2749};
// size of the input arrray
int size = arr.length;
// creating an object of the class IntegerLengthExample2
IntegerLengthExample2 obj = new IntegerLengthExample2();
for(int i = 0; i < size; i++)
{
int count = obj.countDig(arr[i]);
System.out.println("The length of the number " + arr[i] + " is " + count);
}
}
}

Output:

The length of the number 78 is 2
The length of the number 9 is 1
The length of the number 2345 is 4
The length of the number 899009 is 6
The length of the number 1 is 1
The length of the number 414 is 3
The length of the number 34 is 2
The length of the number 1000 is 4
The length of the number 2749 is 4

Using Logarithm

We can also use log to find the length of an integer. Observe the following program.

FileName: IntegerLengthExample3.java

public class IntegerLengthExample3
{
// method to find the number of digits present in the number n
public int countDig(int n)
{
// finding the length of the number n using the log10() method
int len = (int) (Math.log10(n) + 1);
// returning the  length
return len;
}
// main method
public static void main(String argvs[])
{
// input array
int arr[] = {78, 9, 2345, 899009, 1, 414, 34, 1000, 2749};
// size of the input arrray
int size = arr.length;
// creating an object of the class IntegerLengthExample3
IntegerLengthExample3 obj = new IntegerLengthExample3();
for(int i = 0; i < size; i++)
{
int count = obj.countDig(arr[i]);
System.out.println("The length of the number " + arr[i] + " is " + count);
}
}
}

Output:

The length of the number 78 is 2
The length of the number 9 is 1
The length of the number 2345 is 4
The length of the number 899009 is 6
The length of the number 1 is 1
The length of the number 414 is 3
The length of the number 34 is 2
The length of the number 1000 is 4
The length of the number 2749 is 4

Using Recursion

We can also use recursion to find out the length of an integer. The following program demonstrates the same.

FileName: IntegerLengthExample4.java

public class IntegerLengthExample4
{
// method to find the number of digits present in the number n
public int countDig(int n)
{
// handling base case
if(n / 10 == 0)
{
return 1;
}
// recrusively finding the length of the integer n
return 1 + countDig(n / 10);
}
// main method
public static void main(String argvs[])
{
// input array
int arr[] = {78, 9, 2345, 899009, 1, 414, 34, 1000, 2749};
// size of the input array
int size = arr.length;
// creating an object of the class IntegerLengthExample4
IntegerLengthExample4 obj = new IntegerLengthExample4();
for(int i = 0; i < size; i++)
{
int count = obj.countDig(arr[i]);
System.out.println("The length of the number " + arr[i] + " is " + count);
}
}
}

Output:

The length of the number 78 is 2
The length of the number 9 is 1
The length of the number 2345 is 4
The length of the number 899009 is 6
The length of the number 1 is 1
The length of the number 414 is 3
The length of the number 34 is 2
The length of the number 1000 is 4
The length of the number 2749 is 4

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