How to sort an list first letter ascending and last letter decending in java?

Question

I have a list with values

• 1alfreda
• 1alfredb
• 1alfredc
• 2benb
• 2benc
• 2benb

I want the list to be sorted out as first letter ascending and last letter descending so the sorted list is

• 1alfredc
• 1alfredb
• 1alfreda
• 2benc
• 2benb
• 2bena

How can i do it in java ? Plz help.

Answer 1

Not tested it, something like this, should work.

Collections.sort(list, new Comparator<String>() {
  public int compare(String e1, String e2) {
    int c = new Character(e1.chartAt(0)).compareTo( e2.charAt(0) );
    if( c!=0 )
       return c;
    return new Character(e2.chartAt(e2.length()-1)).compareTo( e1.charAt(e1.length()-1) )
  }
});

Answer 2

You could use Collections.sort() and then specify the Comparator where ascending or descending.

List<String> list = new ArrayList<String>();

Collections.sort(list, new Comparator<Item>() {
  @Override
  public int compare(String s1, String o2) {
    return s1.compareTo(s2);
  }
});

Answer 3

It might look like this.

public FirstLetterComparator implements Comparator<String>{
    public int compare(String left, String right){
          String leftFirst = left.substring(0,1);
          String rightFirst = right.substring(0,1);


          return left.compareTo(rightFirst) && ;
    }

}
public LastLetterComparator implements Comparator<String>{
          String leftLast = left.substring(left.length-2,left.length-1);
          String rightLast = right.substring(right.length-2,right.length-1);
         return leftLast.compareTo(rightLast);

}

List<String> yourList = new ArrayList<String>();
Collections.sort(yourList,new FirstLetterComparator());
Collections.sort(yourList,Collections.reverseOrder(new LastLetterComparator()));

There are two different comparators to make it consistent you have to think about one that will be acceptable for your criteria.