# Java Program to Convert Octal Number to Decimal and vice-versa

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

1. `public class DecimalOctal {`
2. ` public static void main(String[] args) {`
3. ` int decimal = 78;`
4. ` int octal = convertDecimalToOctal(decimal);`
5. ` System.out.printf("%d in decimal = %d in octal", decimal, octal);`
6. ` }`
7. ` public static int convertDecimalToOctal(int decimal)`
8. ` {`
9. ` int octalNumber = 0, i = 1;`
10. ` while (decimal != 0)`
11. ` {`
12. ` octalNumber += (decimal % 8) * i;`
13. ` decimal /= 8;`
14. ` i *= 10;`
15. ` }`
16. ` return octalNumber;`
17. ` }`
18. `}`

When you run the program, the output will be:

`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

1. `public class OctalDecimal {`
2. ` public static void main(String[] args) {`
3. ` int octal = 116;`
4. ` int decimal = convertOctalToDecimal(octal);`
5. ` System.out.printf("%d in octal = %d in decimal", octal, decimal);`
6. ` }`
7. ` public static int convertOctalToDecimal(int octal)`
8. ` {`
9. ` int decimalNumber = 0, i = 0;`
10. ` while(octal != 0)`
11. ` {`
12. ` decimalNumber += (octal % 10) * Math.pow(8, i);`
13. ` ++i;`
14. ` octal/=10;`
15. ` }`
16. ` return decimalNumber;`
17. ` }`
18. `}`

When you run the program, the output will be:

`116 in octal = 78 in decimal`

This conversion takes place as:

`1 * 82 + 1 * 81 + 6 * 80 = 78`