Exception in ArrayList in java

Question

public static int getMin(int[] arr, int min,int max,int a){
 Integer[] test = Arrays.stream(arr).boxed().toArray(Integer[]::new);
 List<Integer> list =null;
 list = new ArrayList(Arrays.asList(test));
 list.removeAll(Collections.singleton(0));
 min = Collections.min(list);
 max = Collections.max(list);
 if(a == 0) {
 return min;
 } else {
 return max;
 }
}

List item

Exception in thread "main" java.util.NoSuchElementException
 at java.util.ArrayList$Itr.next(ArrayList.java:862)
 at java.util.Collections.min(Collections.java:596)
 at Solution.getMin(Solution.java:47)

What is the reason for this exception?

• Johannes Kuhn: How many non-0 elements does your list have?
• Shubham Sharma: it depends on input, and for that question inputs are given on runtime
• Holger: As a side note, this is a horribly inefficient way to get the minimum or maximum from an array. Your very first line does already contain a Stream operation, so why not let the Stream return the intended result in the first place: IntStream is = Arrays.stream(arr).filter(i -> i != 0); OptionalInt result = a == 0? is.min(): is.max(); Then, you have to decide what to do if the result is empty, e.g. return result.orElse(0);

Answer 1

Empty collection

The Javadoc for Collections.min states that passing an empty collection will throw a NoSuchElementException.

Add a test for List::isEmpty before checking the minimum and maximum.

Answer 2

You passed an array that contains only zeros. And this line of code removes all zero elements list.removeAll(Collections.singleton(0));. After this, the list has size zero - no any elements in it.

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Here is an example to reproduce the exception

private static void getMin() {
 List<Integer> list = new ArrayList<>();
 Collections.min(list);
}