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

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

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

## Example 1: Program to Convert Binary to Octal

In this program, we will first convert binary number to decimal. Then, the decimal number is converted to octal.

``````public class BinaryOctal {

public static void main(String[] args) {
long binary = 101001;
int octal = convertBinarytoOctal(binary);
System.out.printf("%d in binary = %d in octal", binary, octal);
}

public static int convertBinarytoOctal(long binaryNumber)
{
int octalNumber = 0, decimalNumber = 0, i = 0;

while(binaryNumber != 0)
{
decimalNumber += (binaryNumber % 10) * Math.pow(2, i);
++i;
binaryNumber /= 10;
}

i = 1;

while (decimalNumber != 0)
{
octalNumber += (decimalNumber % 8) * i;
decimalNumber /= 8;
i *= 10;
}

return octalNumber;
}
}``````

Output

`101001 in binary = 51 in octal`

This conversion takes place as:

```Binary To Decimal
1 * 25 + 0 * 24 + 1 * 23 + 0 * 22 + 0 * 21 + 1 * 20 = 41

Decimal to Octal
8 | 41
8 | 5 -- 1
8 | 0 -- 5
(51)
```

## Example 2: Program to Convert Octal to Binary

In this program, the octal number to decimal to decimal at first. Then, the decimal number is converted to binary number.

``````public class OctalBinary {

public static void main(String[] args) {
int octal = 67;
long binary = convertOctalToBinary(octal);
System.out.printf("%d in octal = %d in binary", octal, binary);
}

public static long convertOctalToBinary(int octalNumber)
{
int decimalNumber = 0, i = 0;
long binaryNumber = 0;

while(octalNumber != 0)
{
decimalNumber += (octalNumber % 10) * Math.pow(8, i);
++i;
octalNumber/=10;
}

i = 1;

while (decimalNumber != 0)
{
binaryNumber += (decimalNumber % 2) * i;
decimalNumber /= 2;
i *= 10;
}

return binaryNumber;
}
}``````

Output

`67 in octal = 110111 in binary`

This conversion takes place as:

```Octal To Decimal
6 * 81 + 7 * 80 = 55

Decimal to Binary
2 | 55
2 | 27 -- 1
2 | 13 -- 1
2 | 6  -- 1
2 | 3  -- 0
2 | 1  -- 1
2 | 0  -- 1
(110111)
```