How to switch int sort to String sort?

Question

I have written some code for sorting random integers that a user inputted. How would I switch this into sorting randomly inputted letters? Aka, user inputs j, s, g, w, and the programs outputs g, j, s, w?

for (int i = 0; i < random.length; i++) { //"random" is array with stored integers
                // Assume first value is x
                x = i;
                for (int j = i + 1; j < random.length; j++) {
                    //find smallest value in array (random)
                    if (random[j] < random[x]) {
                        x = j;
                    }
                }
                if (x != i) {
                    //swap the values if not in correct order
                    final int temp = random[i];
                    random[i] = random[x];
                    random[x] = temp;
                }
                itsATextArea.append(random[i] + "\n");// Output ascending order
            }

Originally I hoped (though I knew the chances of me being right were against me) that replacing all the 'int' with 'String' would work...naturally I was wrong and realized perhaps I had to list out what letter came before which by using lists such as list.add("a"); etc.

I apologize if this seems like I am asking you guys to do all the work (which I'm not) but I'm not entirely sure how to start going about this, so if anyone can give some hints or tips, that would be most appreciated!

I swear this is not, my school does not offer this class so I'm trying to learn myself...so oddly enough...I wish this was homework — user2407152
– user2407152, Commented Jun 10, 2013 at 18:52
If you can use the standard libraries, you can simply use Arrays.sort(random): docs.oracle.com/javase/7/docs/api/java/util/… — assylias
– assylias, Commented Jun 10, 2013 at 18:53

mrcaramori · Accepted Answer · 2013-06-10 19:15:05Z

5

You could use String.compareTo() to do that:

Change this:

int[] random = new int[sizeyouhad];
...
if (random[j] < random[x]) {
...
final int temp = random[i];

to:

String[] random = new String[sizeyouhad];
...
if (random[j].compareTo(random[x]) < 0) {
...
final String temp = random[i];

Trial with your code:

String[] random = new String[3];
random[0] = "b";
random[1] = "c";
random[2] = "a";
int x = 0;
//"random" is array with stored integers
for (int i = 0; i < random.length; i++) { 
    // Assume first value is x
    x = i;
    for (int j = i + 1; j < random.length; j++) {
        //find smallest value in array (random)
        if (random[j].compareTo(random[x]) < 0) {
            x = j;
        }
    }
    if (x != i) {
        //swap the values if not in correct order
        final String temp = random[i];
        random[i] = random[x];
        random[x] = temp;
    }
    System.out.println(random[i] + "\n");// Output ascending order
}

edited Jun 10, 2013 at 19:15

answered Jun 10, 2013 at 18:55

mrcaramori

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4 Comments

user2407152 Over a year ago

This is great! However the program still freaks out and the first error being "Exception in thread AWT ....... java,lang.NullPointException"

user2407152 Over a year ago

Should I be declaring an order of the alphabet before all this...?

mrcaramori Over a year ago

You are likely inserting null values on 'random', which will cause you that NullPointerException.

user2407152 Over a year ago

Yes I ending up noticing and was like "oh..." so problem(s) solved and Thank you so much for your help and assistance! =)

Michael Lawrie · Accepted Answer · 2013-06-10 18:54:52Z

0

If you're just trying to sort a list of strings you should probably use the java.util.Collections.sort method rather than writing your own sorting routine.

answered Jun 10, 2013 at 18:54

Michael Lawrie

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1 Comment

User1000547 Over a year ago

I think this is a learning exercise more than anything else. Otherwise, yeah, don't reinvent the wheel.

Santa · Accepted Answer · 2013-06-10 18:56:03Z

0

Was random originally int[]? If you had changed this to String[], you can use String#compareTo method to discern if one string is "less than" another.

Incidentally, you can change the type of random to Comparable[] and then you can use the same algorithm to sort any object whose class implements the interface!

answered Jun 10, 2013 at 18:56

Santa

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Comments

nkukhar · Accepted Answer · 2013-06-10 18:57:21Z

0

Try to use Collections.sort() function

List<String> l = Arrays.asList("j","s", "g","w");
Collections.sort(l);

answered Jun 10, 2013 at 18:57

nkukhar

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Comments

Brett Okken · Accepted Answer · 2013-06-10 18:58:25Z

0

If you consider every character to be a code point[1] and you want to sort by Unicode code point order[2], then there is really no need to change your logic. The work is converting from whatever input you are given (String, char[], etc.) into an int[] of the code points.

[1] - http://docs.oracle.com/javase/6/docs/api/java/lang/String.html#codePointAt(int) [2] - http://en.wikipedia.org/wiki/Code_point

answered Jun 10, 2013 at 18:58

Brett Okken

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Comments

Steve P. · Accepted Answer · 2013-06-10 19:08:13Z

0

You can make your code work on any type of Object by using generics.

answered Jun 10, 2013 at 19:08

Steve P.

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Comments

Gaston Flores · Accepted Answer · 2013-06-10 19:32:53Z

0

The following code is very simple and works perfectly (With this library you can solve your problem in few lines):

import static ch.lambdaj.Lambda.sort;
import static ch.lambdaj.Lambda.on;
import java.util.Arrays;
import java.util.List;

public class Test{
        public static void main(String[] args) {
            List<String> list =  Arrays.asList("1","102","-50","54","ABS");

            List<String> newList = sort(list, on(String.class));
            System.out.println(newList);//[-50, 1, 102, 54, ABS]


}
}

This code uses lambda library (download here, website). Find in the website this example:

List<Person> sorted = sort(persons, on(Person.class).getAge());

answered Jun 10, 2013 at 19:32

Gaston Flores

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