How to convert Octal number to Binary number in Java?

Problem Description :

Write a program in Java that converts Octal number to Binary number.

Octal to Binary conversion

Concept :

For converting octal number to binary number. First, we have to convert octal number to decimal number and then decimal number to binary number.

Octal -> Decimal -> Binary 

Recommended :

How to convert Octal number to Decimal number?

How to convert Decimal number to Binary number?

Java Program :

	package com.javamultiplex.baseconversion;
	import java.util.Scanner;
	/**
	*
	* @author Rohit Agarwal
	* @category Base Conversion
	* @problem Convert Octal to Binary
	*
	*/
	public class OctalToBinary {
	public static void main(String[] args) {
	Scanner input = null;
	try {
	input = new Scanner(System.in);
	System.out.println("Enter octal number : ");
	String number = input.next();
	if (isOctalNumber(number)) {
	String binary = getBinaryFromOctalNumber(number);
	System.out.println("Binary Number : " + binary);
	} else {
	System.out.println("Please enter valid octal number.");
	}
	} finally {
	if (input != null) {
	input.close();
	}
	}
	}
	private static String getBinaryFromOctalNumber(String number) {
	// Convert Octal to Decimal
	int decimal = getDecimalFromOctalNumber(number);
	// Convert Decimal to Binary
	String binary = getBinaryFromDecimalNumber(decimal);
	return binary;
	}
	private static String getBinaryFromDecimalNumber(int decimal) {
	int remainder = 0;
	StringBuilder binary = new StringBuilder();
	while (decimal != 0) {
	remainder = decimal % 2;
	// Converting Integer to String and adding into StringBuilder.
	binary.append(String.valueOf(remainder));
	decimal = decimal / 2;
	}
	// Reverse String using library function of StringBuilder class.
	return binary.reverse().toString();
	}
	private static int getDecimalFromOctalNumber(String number) {
	// Converting String to StringBuilder.
	StringBuilder string = new StringBuilder(number);
	string = string.reverse();
	int length = string.length();
	int digit, power, sum = 0;
	for (int i = 0; i < length; i++) {
	digit = string.charAt(i) - 48;
	power = (int) Math.pow(8, i);
	sum = sum + digit * power;
	}
	return sum;
	}
	private static boolean isOctalNumber(String number) {
	/*
	* Regular expression that matches string containing only octal
	* digits[0-7].
	*/
	String pattern = "^[0-7]+$";
	boolean result = false;
	if (number.matches(pattern)) {
	result = true;
	}
	return result;
	}
	}

view raw OctalToBinary.java hosted with ❤ by GitHub

Output :

Output - How to convert Octal number to Binary number in Java?

References :

https://en.wikipedia.org/wiki/Regular_expression

http://docs.oracle.com/javase/7/docs/api/java/lang/String.html

https://docs.oracle.com/javase/7/docs/api/java/lang/StringBuilder.html

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Tags : Conversion problems, Octal to Binary, Solution in Java, Regular expressions, String, StringBuilder, if else statement, while loop, for loop.

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