Check for duplicate in an ArrayList

Asked Jan 10 '18 at 13:31

Active Jan 10 '18 at 14:02

Viewed 46 times

Im writing a program about animals. The user is supposed to input animal name and age, if the name already exists in the array list they should get an error and be asked to enter a different name. With they code I currently have I can add the same name several times without getting an error. How do I resolve this problem in the easiest way possible?

Edit: the purpose is not to remove the duplicate, but to warn the user that it already exists and ask them to re-enter the name of the animal.

Here is the code:

edited Jan 10 '18 at 14:02

asked Jan 10 '18 at 13:31

1

override the equals method in Animal and use the contains method on the List – Stultuske Jan 10 '18 at 13:33
use a `Set`. It doesn't allow duplicates by default. If you add the same object 2 times, the first will be overwritten – XtremeBaumer Jan 10 '18 at 13:34
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`animalName.contains(animalName)` makes no much sense – Andrew Tobilko Jan 10 '18 at 13:34
@XtremeBaumer that is, if the corresponding class overrides `boolean equals(Object)` (and, correspondlingly, `hashCode()`) – Turing85 Jan 10 '18 at 13:34
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@JuanCarlosMendoza `animalList.add(animal);`. For POJO's the `equals` method has to be `overridden` (true Turing85) – XtremeBaumer Jan 10 '18 at 13:34
You may want to take a look at [`equals(...)` and `hashCode()`](https://docs.oracle.com/javase/tutorial/java/IandI/objectclass.html) since they can simplify your code. – Turing85 Jan 10 '18 at 13:35
@Xtreme you're assuming that equals and hashcode are implemented for hashset to work – OneCricketeer Jan 10 '18 at 13:36

Check for duplicate in an ArrayList

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