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Thread: how to sort arraylist of strings?

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    Default how to sort arraylist of strings?

    hi I have an Array List of <strings> holding phone numbers and index numbers separated by tab
    example:

    45 0876565645
    14 0876476453
    09 0876575657
    111 0876575657
    8211 0876575657

    my question is how would I sort this list in order of first group of numbers while ignoring the phone numbers?
    example:
    09...
    14...
    45...
    111...
    8211...

    any ideas would be great as all I can think of is a load of if statements but this list is 100+ long so that probably wont work


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    Senior Member PhHein's Avatar
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    Default Re: how to sort arraylist of strings?

    Implement a Comparator.

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    Default Re: how to sort arraylist of strings?

    Quote Originally Posted by PhHein View Post
    Implement a Comparator.
    sorry i am a noob but i did look at the comparator class but how would it work without taking into account the phone numbers ?
    i only want to sort them based on the index numbber

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    Default Re: how to sort arraylist of strings?

    Split away the telephone number in the Comparator and just compare the indexes.

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    Default Re: how to sort arraylist of strings?

    Quote Originally Posted by PhHein View Post
    Split away the telephone number in the Comparator and just compare the indexes.

    how ?? didint think that could be done without splitting the list into 2 lists and then joining them together which would just be a big mess is there an inbuilth function for this by the way this is code i am testing on
     ArrayList<String>a=new ArrayList<String>();
            a.add("123    2345462335:454");
            a.add("23    133445645335:454");
            a.add("1783    23456435:454");
            Collections.sort(a);
            for(String h:a){
                System.out.println(h);
            }
    which ouptus
    123    2345462335:454
    1783    23456435:454
    23    133445645335:454

    thanks for help

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    Senior Member PhHein's Avatar
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    Default Re: how to sort arraylist of strings?

    No, you've got the string with the full number, and strings are immutable. So you extract the index into a new String and compare that to another extracted index.

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    Default Re: how to sort arraylist of strings?

    so i am going to have create a bunch of lists and then join em back together DAMB!

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    Senior Member PhHein's Avatar
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    Default Re: how to sort arraylist of strings?

    NOOOO! You leave the list as is. Just extract the index in your compare method.
    public int compare(String no1, String no2) {
    		String index1 = getindex(no1);
    		String index2 = getindex(no2);
    		return index1.compareTo(index2);
    	}
     
    	private String getindex(String no1) {
    		// TODO Auto-generated method stub
    		return null;
    	}

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