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Java Program to Convert Octal to Binary

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  • Difficulty Level : Easy
  • Last Updated : 25 Aug, 2021

Given an Octal number as input, the task is to convert that number into its Binary equivalent number.

Example:

Input: Octal Number = 513
Output: Binary equivalent value is: 101001011

Explanation : 
Binary equivalent value of 5: 101
Binary equivalent value of 1: 001

Binary equivalent value of 3: 011

Octal Number System: 

The Octal number system is a positional numeral system with a radix, or base, of 8 and uses eight distinct digits 0 to 7.

Binary Number System:

A Binary number is a number expressed in the base-2 binary numeral system, which uses only two symbols: which are 0 and 1.

Octal to Binary Conversion Table:

Octal Binary
0 000
1 001
2 010
3 011
4 100
5 101
6 110
7 111

Method 1: Naive Approach

In this approach, the input of Octal number will be taken as a string. Further, the complete string will be iterated character by character and for each character(ie., octal digit), its equivalent binary value according to the above octal to binary conversion table will be evaluated. The result of each iteration will be added in the resultant string and the combination of all values will give the required binary number. Below is the implementation of this approach. 

Java




// Java program to convert
// Octal number to Binary
 
class OctalToBinary {
 
    // function to convert octal number
    // to its binary equivalent value
    static String converter(String octalValue)
    {
 
        // integer variable to iterate
        // the input octal string
        int i = 0;
 
        // string to store the result
        String binaryValue = "";
 
        // iterating the complete length
        // of octal string and assigning
        // the equivalent binary value
        // for each octal digit
        while (i < octalValue.length()) {
 
            // storing character according
            // to the number of iteration
            char c = octalValue.charAt((int)i);
 
            // switch case to check all
            // possible 8 conditions
            switch (c) {
            case '0':
                binaryValue += "000";
                break;
            case '1':
                binaryValue += "001";
                break;
            case '2':
                binaryValue += "010";
                break;
            case '3':
                binaryValue += "011";
                break;
            case '4':
                binaryValue += "100";
                break;
            case '5':
                binaryValue += "101";
                break;
            case '6':
                binaryValue += "110";
                break;
            case '7':
                binaryValue += "111";
                break;
            default:
                System.out.println(
                    "\nInvalid Octal Digit "
                    + octalValue.charAt((int)i));
                break;
            }
            i++;
        }
 
        // returning the final result
        return binaryValue;
    }
 
    // Driver code
    public static void main(String args[])
    {
 
        System.out.println("Octal to Binary Conversion\n");
 
        // octal number which is to be converted
        String octalNumber = "315";
        System.out.println("Octal number: " + octalNumber);
 
        // calling the converter method and
        // storing the result in a string variable
        String result = converter(octalNumber);
 
        System.out.println("Binary equivalent value is: "
                           + result);
    }
}


Output

Octal to Binary Conversion

Octal number: 315
Binary equivalent value is: 011001101

Method 2: Mathematical Approach 

This method involves complete mathematical calculations to obtain the desired result. The input of the Octal number will be taken as an integer. Further, it is first converted into its decimal equivalent value and then from a decimal number to its binary equivalent using mathematical operations. Below is the implementation of this approach.

Java




// Java program to convert
// Octal number to Binary
public class OctalToBinary {
 
    // function to convert octal number
    // to its binary equivalent value
    public static int converter(int octalValue)
    {
 
        // declaring all variable
        // to store the intermediate results
        int i = 0;
        int decimalValue = 0;
        int binaryValue = 0;
 
        // converting octal number
        // into its decimal equivalent
        while (octalValue != 0) {
            decimalValue
                += (octalValue % 10) * Math.pow(8, i);
            ++i;
            octalValue /= 10;
        }
 
        i = 1;
 
        // converting generated decimal number
        // to its binary equivalent
        while (decimalValue != 0) {
            binaryValue += (decimalValue % 2) * i;
            decimalValue /= 2;
            i *= 10;
        }
 
        // returning the final result
        return binaryValue;
    }
 
    // Driver code
    public static void main(String[] args)
    {
 
        System.out.println("Octal to Binary Conversion\n");
 
        // octal number which is to be converted
        int octalNumber = 315;
        System.out.println("Octal number: " + octalNumber);
 
        // calling the converter method and
        // storing the result in a string variable
        int result = converter(octalNumber);
 
        // printing the binary equivalent value
        System.out.println("Binary equivalent value is: "
                           + result);
    }
}


Output

Octal to Binary Conversion

Octal number: 315
Binary equivalent value is: 11001101

Method 3: Using inbuilt java methods

Integer.parseInt() is an in-built function in Java to parse a string into a number system specified by the radix value(2nd argument of the method). In this approach, the input of the Octal number will be taken as a string. The octal string will be parsed into an integer value of octal number system. Further, the octal number will be converted into its binary equivalent using another inbuilt method Integer.toBinaryString(). The resultant value will also be of string datatype. Below is the implementation.

Java




// Java program to convert
// Octal number to Binary
class OctalToBinary {
 
    // function to convert octal number
    // to its binary equivalent value
    public static String converter(String octalValue)
    {
 
        // parsing the string value
        // by following octal number system
        int octal = Integer.parseInt(octalValue, 8);
 
        // converting octal number to binary
        // and storing as a string
        String binaryValue = Integer.toBinaryString(octal);
 
        // returning the resultant string
        return binaryValue;
    }
 
    // Driver code
    public static void main(String args[])
    {
 
        System.out.println("Octal to Binary Conversion\n");
 
        // octal number which is to be converted
        String octalNumber = "315";
        System.out.println("Octal number: " + octalNumber);
 
        // calling the converter method and
        // storing the result in a string variable
        String result = converter(octalNumber);
 
        // printing the binary equivalent value
        System.out.println("Binary equivalent value is: "
                           + result);
    }
}


Output

Octal to Binary Conversion

Octal number: 315
Binary equivalent value is: 11001101

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