Specification for the method (spec it is the same for SE8)

http://docs.oracle.com/javase/7/docs/api/java/util/prefs/AbstractPreferences.html#remove%28java.lang.String%29

says:

Implements the remove(String) method as per the specification in Preferences.remove(String).

While this is not true as

http://docs.oracle.com/javase/7/docs/api/java/util/prefs/Preferences.html#remove%28java.lang.String%29

Specifies assertion

 Throws:
     NullPointerException - if key is null.

Which is not satisfied by java.util.prefs.AbstractPreferences.remove(String)

The specification or the implementation should be updated.

Please see below a code sample illustrating the problem:

---------------------------------------------------------
import java.util.prefs.AbstractPreferences;
import java.util.prefs.BackingStoreException;
import java.util.prefs.Preferences;

public class AbstrPrefNoNPE {

    public static void main(String[] args) {
        ABSTR_PREFS.remove(null);
        System.out.println("Test failure: No NPE was thrown");
    }

    static Preferences ABSTR_PREFS = new AbstractPreferences(null, "") {
        @Override
        protected void putSpi(String key, String value) {
        }
        @Override
        protected String getSpi(String key) {
            return null;
        }
        @Override
        protected void removeSpi(String key) {
        }
        @Override
        protected void removeNodeSpi() throws BackingStoreException {
        }
        @Override
        protected String[] keysSpi() throws BackingStoreException {
            return new String[0];
        }
        @Override
        protected String[] childrenNamesSpi() throws BackingStoreException {
            return new String[0];
        }
        @Override
        protected AbstractPreferences childSpi(String name) {
            return null;
        }
        @Override
        protected void syncSpi() throws BackingStoreException {
        }
        @Override
        protected void flushSpi() throws BackingStoreException {
        }
    };
}
---------------------------------------------------------

The following conformance test will fail due to this problem:

api/java_util/prefs/Preferences/index.html#NPETests[remove]