org.apache.juneau.internal.MultiSet Maven / Gradle / Ivy
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// * to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance *
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// * *
// * http://www.apache.org/licenses/LICENSE-2.0 *
// * *
// * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an *
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package org.apache.juneau.internal;
import static org.apache.juneau.internal.ThrowableUtils.*;
import java.util.*;
/**
* Encapsulates multiple collections so they can be iterated over as if they were all part of the same collection.
*
* @param The object type of this set.
*/
public class MultiSet extends AbstractSet {
/** Inner collections. */
final List> l = new ArrayList<>();
/**
* Create a new Set that consists as a coalesced set of the specified collections.
*
* @param c Zero or more collections to add to this set.
*/
@SafeVarargs
public MultiSet(Collection...c) {
for (Collection cc : c)
append(cc);
}
/**
* Appends the specified collection to this set of collections.
*
* @param c The collection to append to this set of collections.
* @return This object (for method chaining).
*/
public MultiSet append(Collection c) {
assertFieldNotNull(c, "c");
l.add(c);
return this;
}
/**
* Iterates over all entries in all collections.
*/
@Override /* Set */
public Iterator iterator() {
return new Iterator() {
int i = 0;
Iterator i2 = (l.size() > 0 ? l.get(i++).iterator() : null);
@Override /* Iterator */
public boolean hasNext() {
if (i2 == null)
return false;
if (i2.hasNext())
return true;
for (int j = i; j < l.size(); j++)
if (l.get(j).size() > 0)
return true;
return false;
}
@Override /* Iterator */
public E next() {
if (i2 == null)
throw new NoSuchElementException();
while (! i2.hasNext()) {
if (i >= l.size())
throw new NoSuchElementException();
i2 = l.get(i++).iterator();
}
return i2.next();
}
@Override /* Iterator */
public void remove() {
if (i2 == null)
throw new NoSuchElementException();
i2.remove();
}
};
}
/**
* Enumerates over all entries in all collections.
*
* @return An enumeration wrapper around this set.
*/
public Enumeration enumerator() {
return Collections.enumeration(this);
}
@Override /* Set */
public int size() {
int i = 0;
for (Collection c : l)
i += c.size();
return i;
}
}