gistfile1.txt

package org.testing;

import java.util.List;
import java.util.stream.IntStream;

import static java.util.stream.Collectors.counting;
import static java.util.stream.Collectors.groupingBy;
import static java.util.stream.Collectors.toList;

public class Test {

    public static void main(String[] args) {

        // create objects and persist into memory
        List<X> xs = IntStream.range(0, 1_000_000).mapToObj(n -> new X()).collect(toList());

        // count hashes
        System.out.println(xs.stream()
                .collect(groupingBy(System::identityHashCode, counting()))
                .values()
                .stream()
                .filter(sz -> sz > 1)
                .count());
        
    }

    static class X {
    }
}

/* output: 232 */