org.solovyev.common.collections.multiset.AbstractMultiSet Maven / Gradle / Ivy
package org.solovyev.common.collections.multiset;
import java.util.*;
/**
* User: serso
* Date: 7/12/12
* Time: 2:02 PM
*/
public abstract class AbstractMultiSet extends AbstractCollection implements MultiSet {
@Override
public boolean add(E e) {
return this.add(e, 1);
}
@Override
public boolean remove(Object o) {
// if number of elements before was positive then remove() method call must change the collection
return this.remove((E) o, 1) > 0;
}
@Override
public boolean removeAll(Collection c) {
boolean modified = false;
for (Object o : c) {
modified = modified | this.remove(o);
}
return modified;
}
@Override
public boolean retainAll(Collection c) {
boolean modified = false;
for (E e : toElementSet()) {
if (!c.contains(e)) {
modified = modified | remove(e);
}
}
return modified;
}
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj instanceof MultiSet) {
final MultiSet that = (MultiSet) obj;
if (this.size() == that.size()) {
boolean equals = true;
for (E e : this) {
if ( this.count(e) != that.count(e) ) {
equals = false;
break;
}
}
return equals;
}
}
return false;
}
@Override
public int hashCode() {
// not good solution but still better than nothing.
// Problem: set doesn't require any particular order of it's elements, for equals method it is not significant information
// however hashCode method depends on each implementation of multiset and use the order of elements returned by iterator
// Solution (used): get all the hash codes of all elements in the multiset, sort them and then sum ()
// Solution (not used): demand from the subclass specific order of it's elements
final List hashCodes = new ArrayList(this.size());
for (E e : this) {
hashCodes.add(e == null ? 0 : e.hashCode());
}
Collections.sort(hashCodes);
int result = 1;
for (Integer hashCode : hashCodes) {
result = 31 * result + hashCode;
}
return result;
}
}