Searchable, maintains insertion order, mutable

declare new array list

List<Integer> scores = new ArrayList<>();

access the scores list; remove last item: scores.remove(length-1);

access the scores list; access last item and add 2x: scores.add(Integer.valueOf(scores.get(length-1) * 2));

ArrayList

Import java.util.ArrayList

List<Integer> result = new ArrayList<>();

result.add(0); <= Initialize 0’s or add numbers if need change

Length: a.size()

Access: a.get(i)

Change item: a.set(0, 5) (index, changeto)

Remove: a.remove(0);

Clear: a.clear();

#items: a.size();

Sort: Collections.sort(a)

ArrayList<Integer> a

Sort: Collections.sort(a)

Create a hashmap: Map<Integer, Integer> differences = new HashMap<>();

Add differences into it: for (int i = 0; i < arr.length-1; i++){

differences.put(arr[i], arr[i+1]-arr[i]); }

Int minDiff = Integer.Max_Value; // set a value to a giant number to calc minimum

Add to frequencyMap: frequencyMap.put(num, frequencyMap.getOrDefault(num,0) +1);

Find the value in freqMap of 1: map over freqMap:if (frequencyMap.get(num) == 1)

for (int num : freqMap.keySet()) { // map over freqMap

if (freqMap.get(num) > 1) { // if freq > 1

dups.add(num); // add to ArrayLlist

}

}