FULL PRODUCT VERSION :

C:\tools\Java\jdk1.8.0_45\bin>java -version
java version "1.8.0_45"
Java(TM) SE Runtime Environment (build 1.8.0_45-b15)
Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Window 7 64 bit.

A DESCRIPTION OF THE PROBLEM :
Hi Team

We have an issue related to removeAll() implementation of Map in Java 8. As per the current implementation we are iterating the whole data structure to remove a single or no element (If the collection passed doesn't have any element).

Please review the attached sample code and do a JVisual VM profiling.





 

REGRESSION. Last worked in version 8u73

ADDITIONAL REGRESSION INFORMATION:
C:\tools\Java\jdk1.8.0_45\bin>java -version
java version "1.8.0_45"
Java(TM) SE Runtime Environment (build 1.8.0_45-b15)
Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Sample code and JVisualVM profiler snapshot attached.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Should work similar to JDK 7 logic. In order to remove a single entry we must not iterate the whole data structure.

public boolean removeAll(Collection<?> c) {
        boolean modified = false;

        if (size() > c.size()) {
            for (Iterator<?> i = c.iterator(); i.hasNext(); )
                modified |= remove(i.next());
        } else {
            for (Iterator<?> i = iterator(); i.hasNext(); ) {
                if (c.contains(i.next())) {
                    i.remove();
                    modified = true;
                }
            }
        }
        return modified;
    }
ACTUAL -
 In order to remove a single entry we must not iterate the whole data structure.
public final boolean removeAll(Collection<?> c) {
            if (c == null) throw new NullPointerException();
            boolean modified = false;
            for (Iterator<E> it = iterator(); it.hasNext();) {
                if (c.contains(it.next())) {
                    it.remove();
                    modified = true;
                }
            }
            return modified;
        }

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
public class TestConcurrentHashMap {

public static void main(String[] args) {
Map<Integer, Integer> map = new ConcurrentHashMap<Integer, Integer>();

for (int i=0; i<10000000; i++) {
map.put(i, i);
}

List<Integer> oList = new ArrayList<Integer>();
oList.add(9998);
oList.add(9999);

map.keySet().removeAll(oList);
System.out.println(map);
}

}

---------- END SOURCE ----------