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Implementation of the collection facilities.
package fr.vergne.collection.util;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
/**
* A {@link ComposedKey} is an utilitary class to compose several pieces of data
* in a single one and use this composition as a key, for instance in a
* {@link Map}. Such a key need to be considered as equal to another if both
* provide the same composition. Thus, the {@link #equals(Object)} and
* {@link #hashCode()} methods have been overriden consequently. For consistency
* reasons, a {@link ComposedKey} is made as an immutable object, so it is not
* possible to change the data it composes.
*
* @author Matthieu Vergne
*
* @param
*/
public class ComposedKey implements Iterable {
private final List keys;
public ComposedKey(List keys) {
this.keys = Collections.unmodifiableList(new ArrayList(keys));
}
@SuppressWarnings("unchecked")
public TT get(int index) {
return (TT) keys.get(index);
}
public int size() {
return keys.size();
}
@Override
public Iterator iterator() {
return keys.iterator();
}
@Override
public boolean equals(Object obj) {
if (obj == this) {
return true;
} else if (obj instanceof ComposedKey) {
ComposedKey k = (ComposedKey) obj;
Iterator iterator1 = iterator();
Iterator iterator2 = k.iterator();
while (iterator1.hasNext() && iterator2.hasNext()) {
Object key2 = iterator2.next();
T key1 = iterator1.next();
if (key1 == key2 || key1 != null && key1.equals(key2)) {
// still the same
} else {
return false;
}
}
return !iterator1.hasNext() && !iterator2.hasNext();
} else {
return false;
}
}
@Override
public int hashCode() {
int hash = 1;
for (T key : keys) {
hash *= key.hashCode();
}
return hash;
}
}