Re: Finding Duplicate Values In An Array List

From:

Robert Klemme <shortcutter@googlemail.com>

Newsgroups:

comp.lang.java.programmer

Date:

Thu, 10 Jul 2014 19:24:08 +0200

Message-ID:

<c280hpF266aU1@mid.individual.net>

On 09.07.2014 16:47, Daniele Futtorovic wrote:

Here's another, shorter one:

public static void main(String[] ss){
   Scanner sc = new Scanner(System.in);
   Set<Integer> sieve = new HashSet<Integer>();
   List<Integer> stash = new ArrayList<Integer>(20);

   while( stash.size() < 20 ){
     System.err.printf( "Enter %d more number(s) between 10 and 100:%n",
20 - stash.size() );
     String raw = sc.next();

     try {
       int input = Integer.parseInt(raw);

       if( input < 10 || input > 100 ){
         System.err.println( "Out of range: " + input );
       }
       else if( ! sieve.add( input ) ){
         System.err.println( "Duplicate: " + input );
       }
       else {
         stash.add( input );
         System.err.println( stash );
       }
     }
     catch( NumberFormatException nfex ){
       System.err.println( "Not a number: " + raw );
     }
   }

Similar amount of lines, but differently distributed

package golf;

import java.util.BitSet;
import java.util.Scanner;

public class FiDuWa {

   private static final int LIMIT = 20;
   private static final int MIN = 10;
   private static final int MAX = 100;

   public static void main(String[] args) {
     @SuppressWarnings("resource")
     final Scanner scan = new Scanner(System.in);
     final StringBuilder stash = new StringBuilder();
     final BitSet used = new BitSet();

     while (used.cardinality() < LIMIT) {
       final int i = Integer.parseInt(scan.next());

       if (i >= MIN && i <= MAX) {
         if (!used.get(i)) {
           if (!used.isEmpty())
             stash.append(' ');

           stash.append(i);
           used.set(i);
           System.out.println(stash);
         } else
           System.err.println("Duplicate: " + i);
       } else {
         System.err.println("Not in range: " + i);
       }
     }
   }
}

The Java standard library is a remarkable beast and BitSets are probably
underused.

Kind regards

    robert