import java.util.ArrayList;
import java.util.HashMap;
import java.util.Spliterator;
import java.util.function.Consumer;
import java.util.function.UnaryOperator;

/*
 * HashMap spliterator tryAdvance() encounters remaining elements after a
 * forEachRemaining() call.
 */
public class ObjSplitter {
    private final static int COUNT = 1000;
    // With smaller COUNT, error happens only intermittently
    // private final static int COUNT = 12;

    public static void main(String[] args) {
        HashMap<String,String> map = new HashMap<>();
        
        for (int i = 0; i < COUNT; i++) {
            String keyVal = new String("String" + i);
            map.put(keyVal, keyVal);
        }
        Spliterator splitter = map.keySet().spliterator();
        // When loop covers more of the colleciton, the error seems to happen less often
        // for (int i = 0; i < COUNT / 2; i++) {
      // for (int i = 0; i < COUNT / 2 - 1; i++) {
        for (int i = 0; i < 10; i++) {
            splitter.tryAdvance(b -> System.out.println("tryAdvance: " + b));
        }
        // finish it
        splitter.forEachRemaining(b -> System.out.println("forEachRemaining: " + b));

        // Confirm there are no more elements
        splitter.forEachRemaining(b -> fail("forEachRemaining should have no elements: " + b));
        splitter.tryAdvance(b -> fail("tryAdvance should have no elements: " + b));
    }
    
    public static void fail(String msg) {
        throw new Error(msg);
    }
}