In this tutorial, we will write a program to convert octal to decimal in java. Before that, you must have knowledge of the following topics in C++.

**Octal number**

The octal numbers are the numbers with base 8 and use the digits 0 to 7. Example: 8 in decimal is represented as 10 in octal, 25 as 31, and so on.

**Decimal Number**

These are the numbers with a base of 10, which ranges from 0 to 9. These numbers are formed with the combination of 0 to 9 digits such as 24, 345, etc.

Conversion example:

`Input: 23`

Output: 19

Let us go through a program for the octal to decimal Conversion in java.

**Java Program to Convert Octal to Decimal using while loop**

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 | import java.util.Scanner; public class Main { public static void main(String[] args) { int octalNum, decimalNumber = 0, i = 0; Scanner scan = new Scanner(System.in); System.out.print("Enter an Octal Number: "); octalNum = scan.nextInt(); while (octalNum != 0) { decimalNumber += (octalNum % 10) *Math.pow(8, i); ++i; octalNum /= 10; } System.out.printf("Equivalent Decimal Number: %d", decimalNumber); } } |

**Output:**

`Enter an Octal Number: 23`

Equivalent Decimal Number: 19