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

To understand this example, you should have the knowledge of the following Java programming topics:

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