import java.util.List; import java.util.ArrayList; import java.util.Map; import java.util.TreeMap; import java.util.Random; public class Main { public static void main(String[] args) { List<Integer> myInts = new ArrayList<>(); Random random = new Random(); for(int i =0; i < 20; i++) { myInts.add(random.nextInt(5)); } Map<Integer, Integer> intCount = countNumbers(myInts); for(Map.Entry<Integer, Integer> entry: intCount.entrySet()) { System.out.println("Integer: "+ entry.getKey()+" appears: "+ entry.getValue()); } } public static Map<Integer, Integer> countNumbers(List<Integer> list) { Map<Integer, Integer> intCount = new TreeMap<>(); for(Integer i: list){ Integer currentCount = intCount.get(i); if(currentCount!=null){ int newCount = currentCount+1; intCount.put(i, newCount);} else{intCount.put(i, 1);} } return intCount; } } /* Output: Integer: 0 appears: 3 Integer: 1 appears: 2 Integer: 2 appears: 8 Integer: 3 appears: 1 Integer: 4 appears: 6
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