将一串字母转换为数字

Question

So I'm new to computer science and one of the things we've been asked to do is to attempt to create a program that firstly converts a word inputted by the user into a string of numbers, with a=1, b=2, z=26 etc. along with some other things which I wont go into now as they're extension. Admittedly she says she doesn't mind if we complete it as it was our first proper java lesson today.

So in light of that, can anyone give me any tips on how to do this? I don't want a complete piece of code to do exactly that as I need to learn and so a guiding hand instead would be greatly appreciated. What I have written so far:

import java.util.*;
public class main
{
 /**
 * Constructor for objects of class main
 */
public static void main(String [ ] args)
{
    Scanner keyboard = new Scanner(System.in);
    String word = "";
    System.out.print("\nPlease enter a word: ");
    word = keyboard.nextLine();
    for(int i=0; i<word.length(); i++)
    {

    }
}

There's pretty much nothing there I know, but as mentioned we haven't exactly learnt anything yet so that's all I've managed to get in so far, and to be honest there's probably something wrong there already.

My assumption is there's a way for me to convert each letter to it's number (maybe the numbers are already assigned to letters in Java?) in a for loop. My only other idea is to convert it to an array, have another array with the numbers in and find a way to output the relevant counterpart. But I'm not sure.

Thanks!

Anthony

Answer 1

You can subtract two char variables. This gives the difference between their ASCII values.

for(int i=0; i<word.length(); i++)
{
    char c = word.charAt(i);
    System.out.println(c - 'a' +1);
}

Answer 2

Suppose you've read a String and need a int[] array where every number corresponds to letter in from a = 1 to z = 26 :

public int[] toNumbers(String s) {
    if (s == null)
        return null;
    int[] r = new int[s.length()];
    int i = 0;
    for (char c : s.toLowerCase().toCharArray())
       r[i++] = c - 'a' + 1;
    return r;
}

To print result, just use Arrays.toString() :

System.out.println(Arrays.toString(r));

Answer 3

Try to use parseInt for int variable & parseDouble for double variable for eg String num1 = "123"; /* <-- it's a string no a number */ String num2 = "2.3"; int x = Integer.parseInt(num1); /* String is converted to int */ int y = Double.parseDouble(num2); /* String is converted to double */ String num1 = "123"; /* <-- it's a string no a number */ String num2 = "2.3"; int x = Integer.parseInt(num1); /* String is converted to int */ int y = Double.parseDouble(num2); /* String is converted to double */ String num1 = "123"; /* <-- it's a string no a number */ String num2 = "2.3"; int x = Integer.parseInt(num1); /* String is converted to int */ int y = Double.parseDouble(num2); /* String is converted to double */ .