# Java Program to Convert Octal to Binary

• 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:

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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