In this program, you’ll learn to convert octal number to a decimal number and vice-versa using functions in Java.

## Example 1: Program to Convert Decimal to Octal

public class DecimalOctal { public static void main(String[] args) { int decimal = 78; int octal = convertDecimalToOctal(decimal); System.out.printf("%d in decimal = %d in octal", decimal, octal); } public static int convertDecimalToOctal(int decimal) { int octalNumber = 0, i = 1; while (decimal != 0) { octalNumber += (decimal % 8) * i; decimal /= 8; i *= 10; } return octalNumber; } }

**Output**

78 in decimal = 116 in octal

This conversion takes place as:

8 | 78 8 | 9 -- 6 8 | 1 -- 1 8 | 0 -- 1 (116)

## Example 2: Program to Convert Octal to Decimal

public class OctalDecimal { public static void main(String[] args) { int octal = 116; int decimal = convertOctalToDecimal(octal); System.out.printf("%d in octal = %d in decimal", octal, decimal); } public static int convertOctalToDecimal(int octal) { int decimalNumber = 0, i = 0; while(octal != 0) { decimalNumber += (octal % 10) * Math.pow(8, i); ++i; octal/=10; } return decimalNumber; } }

**Output**

116 in octal = 78 in decimal

This conversion takes place as:

1 * 8^{2}+ 1 * 8^{1}+ 6 * 8^{0}= 78