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| Remove Duplicates from ArrayList |
We use
ArrayList a lot but what if we want to remove duplicates from
ArrayList with an easy method.There are other cumbersome ways to do this by iterating through
ArrayList and removing etc, but here i will use another easy way to remove repeated values in
ArrayList, that is by using another collection called
Set.
Set is a collection which does not allow insertion of duplicate values in to it.So under
Set Collection there are two candidates which can do this job they are
HashSet and
LinkedHashSet.
HashSet does not retain order of elements inserted to it while
LinkedHashSet preserve the order, so you can use either of the one based on your situation, here i will use
LinkedHashSet so i can preserve the order of elements as same as its seen in my
ArrayList.
So the steps to do that are
1.Copy all the elements in our duplicated
ArrayList to a
LinkedHashSet.
2.Now clear all the values in our duplicated
ArrayList and fill it back with non duplicated values from
LinkedHashSet.
Code in Action below!
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| List<String> arrayListObject = new ArrayList<>();
// adding elements to arrayListObject, including duplicates,Total 5 elements
arrayListObject.add("London");
arrayListObject.add("Paris");
arrayListObject.add("Tokyo");
arrayListObject.add("London");
arrayListObject.add("Paris");
Set<String> hashSetObject = new LinkedHashSet<>();//Note here we use LinkedHashSet
hashSetObject.addAll(arrayListObject);//Adding ArrayList values to LinkedHashSet, duplicates removed
arrayListObject.clear();//Clearing all values in ArrayList
arrayListObject.addAll(hashSetObject);//Filling ArrayList back with non duplicated values, now it has 3 elements
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I am a Java and Android developer and a science enthusiast.I Like to explain complex things in simple language so anybody even without a graduation in computer science or Electronics can understand the concepts easily.
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