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.

Are you forced to use an array? Could you just use a HashSet which would not allow duplicates in the first place. — Michael J. Lee, May 31 '15 at 11:46

Leon · Answer 1 · 2015-05-31T11:49:27.407

5

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()]);

edited May 31 '15 at 11:49

answered May 31 '15 at 11:46

Leon

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or LinkedHashSet to preserve order – Robert May 31 '15 at 11:48
It's Working ..Thanks a Lot – JayaSantoshKumar May 31 '15 at 12:54

Rich · Answer 2 · 2015-05-31T13:16:36.287

Your question raises a few points:

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));

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);
```
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.

Your code is good ... Using LinkedHashSet we can get sorted list — JayaSantoshKumar, May 31 '15 at 13:07

score 1 · Answer 3 · answered May 31 '15 at 12:32

1

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);

answered May 31 '15 at 12:32

Tagir Valeev

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Your code is too simplified Thanks buddy :) It's working – JayaSantoshKumar May 31 '15 at 13:16

score 1 · Answer 4 · answered May 31 '15 at 12:42

1

this will work simply

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

answered May 31 '15 at 12:42

Rajan Kali

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Wow Rajan Thanks a Lot .. Your's code is simplified too. – JayaSantoshKumar May 31 '15 at 13:18

How to delete similar elements from String array or ArrayList

4 Answers4