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Write a Java program to convert binary numbers to decimal numbers.

  1. Jul 18, 2012 #1
    Use a loop to read (charAt()) each digit (0/1 char) in the input string, scanning from right to left;

    Use the loop to build the required powers of 2;

    Use a conditional statement to deal with 0 and 1 separately;

    Debug using simple input, e.g. 1, 10, 101, and print intermediate values in the loop.

    Use your program to find the decimal value of the following binary number:


    I have got as far as this:

    import java.lang.*;
    import java.io.*;

    public class BinaryToDecimal{
    public static void main(String[] args) throws IOException{
    BufferedReader bf= new BufferedReader(new InputStreamReader(System.in));
    System.out.print("Enter the Binary value: ");
    String str = bf.readLine();
    long num = Long.parseLong(str);
    long rem;
    while(num > 0){
    rem = num % 10;
    num = num / 10;
    if(rem != 0 && rem != 1){
    System.out.println("This is not a binary number.");
    System.out.println("Please try once again.");
    int i= Integer.parseInt(str,2);
    System.out.println("Decimal:="+ i);

    But when I compile and run it only says "Enter the Binary value:"
    Help! :/
  2. jcsd
  3. Jul 18, 2012 #2


    Staff: Mentor

    When you post code, put [noparse] a
    Code (Text):
     tag at the top and a
    [/noparse] tag at the bottom. This preserves your indentation, if any, and makes your code easier to read. I have done this below.

    Since you didn't do much indentation, I have done so.
    After your program printed "Enter the Binary value:" did you enter a binary value?
  4. Jul 18, 2012 #3
    Thank you so much
    Im new to this so I dont know how to use it much :S
    No, I couldnt enter the Binary Number because im using netbeans
    How is it possible to enter the number? Do i just type it in next to "Enter Binary Number" ?
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