Binary Conversion in Java

Question

Before implementing a GUI I tried performing it at CLI first and I also tried to implement it by using calling methods to another class.

BinaryConversion class:

import java.io.IOException;
import static java.lang.System.in;
import java.util.InputMismatchException;
import java.util.Scanner;
public class BinaryConversion{
 public static void main(String[] args) throws IOException {
 try (Scanner in = new Scanner(System.in)) {
 System.out.print("Enter given: ");
 int givenNum = in.nextInt();
 System.out.println("Binary: " + convert.getBinary(givenNum));
 System.out.println("Octal: " + convert.getOctal(givenNum));
 System.out.println("Hex: " + convert.getHex(givenNum));
 } catch(InputMismatchException e) {
 System.out.println("Looks like you entered a non integer value.");
 } finally {
 in.close();
 }
 }
}

Convert class:

public final class convert{
 private convert() {
 // removes the default constructor
 }
 public static String getBinary(int given) {
 char binNumbers[] = {'0','1'}; 
 String str = "";
 int rem;
 while (given > 0) {
 rem = given % 2;
 str = binNumbers[rem] + str;
 given /= 2;
 }
 return str;
 }
 public static String getOctal(int given) {
 char octalNumbers[] = {'0','1','2','3','4','5','6','7'}; 
 String str = "";
 int rem;
 while (given > 0) {
 rem = given % 8;
 str = octalNumbers[rem] + str;
 given /= 8;
 } 
 return str;
 }
 public static String getHex(int given) {
 char hexNumbers[] = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
 String str = "";
 int rem;
 while(given > 0){
 rem = given % 16;
 str = hexNumbers[rem] + str;
 given /= 16;
 }
 return str;
 }
}

My questions are:

• Did I missed something?
• Is there a more efficient implementation of this program?

• h.j.k.: Related: Integer.toString(int, int)

Answer 1

First: Please format your code more consistently.

The indention of the whileloop is very unusual. Better (and more common):

public static String getBinary(int given) {
 char binNumbers[] = {'0','1'}; 
 String str = "";
 int rem;
 while (given > 0) {
 rem = given % 2;
 str = binNumbers[rem] + str;
 given /= 2;
 }
 return str;
}

Next: Please use the default cases for identifiers. Classes should start upper case (Convert instead of convert).

Also use StringBuilder instead of String-concatenation:

public static String getBinary(int given) {
 char binNumbers[] = {'0','1'}; 
 StringBuilder sb = new StringBuilder();
 int rem;
 while (given > 0) {
 rem = given % 2;
 sb.append(binNumbers[rem]);
 given /= 2;
 }
 return sb.toString();
}

Ths will be a large performace gain. Your code basically translates to:

public static String getBinary(int given) {
 char binNumbers[] = {'0','1'}; 
 String str = "";
 int rem;
 while (given > 0) {
 rem = given % 2;
 //str = binNumbers[rem] + str;
 // Code generated by compiler for the above line of code
 StringBuffer sb = new StringBuffer();
 sb.append(binNumbers[rem]);
 sb.append(str);
 str = sb.toString();
 // End of generated code
 given /= 2;
 }
 return str;
}

As you can see the code generated many objects which have to be cleaned up afterwards by the Garbage Collector.

Hint:

You can use Integer.toString(given, 2) instead of your Convert.getBinary(given) for the same result.

Answer 2

I have already stated the obvious in my comment, so I'll focus on the other parts of your code.

It's nice that you know how to use try-with-resources, but that also means you don't need the finally clause.

Your convert class should be Converter (note the title case), and your comment here is misleading:

private convert() {
 // removes the default constructor
}

Yes, it's understood that utility classes often do not have a public constructor, so you should either mention something to that extent, or just put a dummy comment (more to suppress empty code block warnings for the latter):

private Converter() {
 // utility class do not need public constructor
}

As for your actual conversion implementations, note that they tend to follow the pattern:

• declare a char[] array of valid outputs
• perform a modulus based on the length of the char[] array
• perform an integer division and loop till this yields 0

As such, you can probably have the following private static method to standardize this:

private static String doConvert(int input, char[] values) {
 int base = values.length; // 2, 8, 16
 int rem;
 // ...
}
// illustration
public static String toBinary(int given) {
 // can consider putting new char[]{'0','1'} as a static field too
 return doConvert(given, new char[]{'0','1'});
}