Converting decimal to binary in Java

Question

I\'m trying to write a code that converts a number to binary, and this is what I wrote. It gives me couple of errors in Eclipse, which I don\'t understand. What\'s wrong wit

Answer 1

Maybe you don't want to use toBinaryString(). You said that you are learning at the moment, so you can do it yourself like this:

/*
  F:\>java A 123
  123
    1  1  0  1  1  1  1  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
  0  0  0  0  0  0
*/

public class A {
    public static void main(String[] args) {

        int a = Integer.parseInt(args[0]);
        System.out.println(a);

        int bit=1;
        for(int i=0; i<32; i++) {
            System.out.print("  "+(((a&bit)==0)?0:1));
            bit*=2;
        }
    }
}

Answer 2

package gg;

import java.util.*;

public class Gg {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        boolean flag = true;
        while (flag) {
            menu();
            int n = in.nextInt();
            switch (n) {
            case 1:
                System.out.println("enter an integer decimal number : ");
                int d = in.nextInt();
                System.out.print("the answer is ");
                DTB(d);
                System.out.println();
                break;
            case 2:
                System.out.println("enter a binary number : ");
                int b = in.nextInt();
                System.out.print("the answer is " + BTD(b));
                System.out.println();
                break;
            case 3:
                flag = false;
                break;
            }
        }
    }

    public static void menu() {
        System.out.println("1.convert decimal to binary : ");
        System.out.println("2.convert binary to decimal : ");
        System.out.println("3.exit");
    }

    public static void DTB(int x) {
        int n = 0;
        int y = x;
        while (y > 0) {
            y /= 2;
            n++;
        }
        int s[] = new int[n];
        int i = 0;
        while (x > 0) {
            s[i] = x % 2;
            x /= 2;
            i++;
        }
        for (int j = s.length - 1; j >= 0; j--) {
            System.out.print(s[j]);
        }
    }

    public static int BTD(int x) {
        int y = 2;
        int sum = 0;
        double k = 1;
        int c = 0;
        while (x > 0) {
            double z = x % 10;
            x /= 10;
            k = Math.pow(y, c);
            c++;
            k *= z;
            sum += k;
        }
        return sum;
    }

}

Answer 3

I suggest you get your program to compile first in your IDE. If you are not using an IDE I suggest you get a free one. This will show you where your errors are and I suggest you correct the errors until it compiles before worring about how to improve it.

Answer 4

Well, first I assume you know about error messages. Second, your code is bleak (syntax and indentation is not correct). I would suggest the code below,

import java.util.Scanner;

public class IntToBinary
{
   public static void main(String[] args)
   {
      int number = 0;
      Scanner sc = new Scanner(System.in);
      System.out.println("Please enter an integer : ");
      number = sc.nextInt(); 
      convertToBinary(number);
      sc.close();
   }

   public static void convertToBinary(int num)
   {
      String str = "";
      for(int a = 0; a < 8; a++)
      {
         if(num % 2 == 1)
         {
            str = "1" + str;
         }
         if(num % 2 == 0)
         {
            str = "0" + str;
         }
         num = num / 2;
      }
      System.out.println("The binary conversion is : " + str);
   }
}

Hope it helps!!

Answer 5

For starters you've declared a method inside a method. The main method is the method that runs first when you run your class. ParseInt takes a string, whereas args is an Array of strings, so we need to take the first (0-based) index of the array.

mod is not a valid operator, the syntax you wanted was %

You can use System.out.print to print on the same line rather than println

Try these corrections and let me know how you get on:

 public class NumberConverter {
  public static void main(String[] args) {
  int i = Integer.parseInt(args[0]);
  Binary(i);
 } 

 public static void Binary(int int1){
    System.out.println(int1 + " in binary is ");
    do {
        System.out.print(int1 % 2);
        int1 /= 2;
    } while (int1 > 0);


 }
}

Answer 6

Integer.toBinaryString(int) should do the trick !

And by the way, correct your syntax, if you're using Eclipse I'm sure he's complaining about a lot of error.

Working code :

public class NumberConverter {
   public static void main(String[] args) {
       int i = Integer.parseInt(args[0]);
       toBinary(i);
   }

   public static void toBinary(int int1){
       System.out.println(int1 + " in binary is");
       System.out.println(Integer.toBinaryString(int1));
   }
}