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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.

class Main {
  public static void main(String[] args) {
    long binary = 101001;
    int octal = convertBinarytoOctal(binary);
    System.out.println(binary + " in binary = " + octal + " in 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.

class Main {
  public static void main(String[] args) {
    int octal = 67;
    long binary = convertOctalToBinary(octal);
    System.out.println(octal + " in octal = " + binary + " in 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)