Java sorting an String Array by a Substring of characters

Question

I need to sort an array of strings like the following, by a substring of characters:

[0] = "gtrd3455";
[1] = "wsft885";
[2] = "ltzy96545";
[3] = "scry5558";
[4] = "lopa475";

I need to sort by the following "3455, 885, 96545, 5558, 475" I need to substring off the first 4 characters of the array, sort it and display back in an array like the output below.

The output should be an array like:

[0] = "ltzy96545";
[1] = "scry5558";
[2] = "gtrd3455";
[3] = "wsft885";
[4] = "lopa475";

Example of how I can do this in Java?

Rohit Jain · Accepted Answer · 2012-10-24 19:41:18Z

9

You can use a Comparator, and use Array#sort method with it, to sort it according to your need: -

String[] yourArray = new String[3];
yourArray[0] = "gtrd3455";
yourArray[1] = "ltzy96545";
yourArray[2] = "lopa475";

Arrays.sort(yourArray, new Comparator<String>() {
    public int compare(String str1, String str2) {
        String substr1 = str1.substring(4);
        String substr2 = str2.substring(4);

        return Integer.valueOf(substr2).compareTo(Integer.valueOf(substr1));
    }
});

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

OUTPUT: -

[ltzy96545, gtrd3455, lopa475]

edited Oct 24, 2012 at 19:41

answered Oct 24, 2012 at 19:23

Rohit Jain

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4 Comments

Rohit Jain Over a year ago

@NullUserException. Also You missed a valid error though. I used compareTo on Integer.parseInt. which returns primitive int. ;)

Jsn0605 Over a year ago

How can I read in lines of a text file and add each line to the string array? Then do the sorting based on that dynamic array.

Rohit Jain Over a year ago

@Jsn0605 For that you need to first fill your Array from the text file. And then the remaining process is same.

Rohit Jain Over a year ago

@Jsn0605. I would suggest to use an ArrayList rather. Because you don't know how many lines you would get from the file.

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