How to delete similar elements from String array or ArrayList

Question

I'm totally new to programming and I have String array:

String dates[] = {"01-01-1993", "19-11-1993", "01-01-1993", "03-03-2000", "03-03-2000"};

In the above array dates[0] == dates[2] and dates[3] == dates[4], I want to delete the duplicate values which IS REPEATED and I want program to produce result like this:

dates[] = {"01-01-1993", "19-11-1993", "03-03-2000"}

Some are using ArrayList concept some are using complex for loops and I'm confused, so could you please help in achieving the above task.

Thanks In Advance.

Answer 1

You can use a Set to remove duplicates.

Set<T> dateSet = new HashSet<T>(Arrays.asList(dates));

dateSet will only contain unique values.

If you need to get back to an array

dates = dateSet.toArray(new String[dateSet.size()]);

Answer 2

Your question raises a few points:

1. In general, this kind of manipulation of collections is much easier and cleaner if you use the Collection classes (Set, List, etc). For example, a Set guarantees uniqueness of the elements:

   String dates[] = {"01-01-1993", "19-11-1993","01-01-1993","03-03-2000","03-03-2000"};
   Set<String> uniqueDates = new HashSet<>(Arrays.asList(dates));
   

But HashSet is unordered; if you iterate over uniqueDates the order in which you get the back is arbitrary. If the order is important, you could use LinkedHashSet:

Set<String> orderedUniqueDates = new LinkedHashSet<>(Arrays.asList(dates));

2. The basic collection that come with Java are pretty good; but if you use Google's Guava library (https://github.com/google/guava), it gets really nice and you can do really powerful things like finding intersections of sets, set differences etc.:

   Set<String> uniqueDates = Sets.newHashSet(dates);
   

3. More fundamentally, String is a very poor choice of data type to represent Dates. Consider using either java.util.Date or (if using a Java version prior to 8) org.joda.time.DateTime (http://www.joda.org/joda-time/). Not only will this give you type safety and ensure that your data is really all dates, but you could then do things like sorting.

Answer 3

Using Java 8 you can do the following:

String dates[] = {"01-01-1993", "19-11-1993", "01-01-1993", "03-03-2000", "03-03-2000"};
dates = Arrays.stream(dates).distinct().toArray(String[]::new);

Answer 4

this will work simply

 Set<T> tempSet= new HashSet<T>(Arrays.asList(dates));
    String[] dates= tempSet.toArray(new String[tempSet.size()]);//copy distinct values