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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* 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
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.tuscany.sca.common.java.collection;
import java.util.Enumeration;
import java.util.NoSuchElementException;
public class CompoundEnumeration<T> implements Enumeration<T> {
private Enumeration<T>[] enumerations = null;
private int index = 0;
public CompoundEnumeration(Enumeration<T>... enums) {
enumerations = enums;
}
public boolean hasMoreElements() {
// if the current enum is null that means this enum is finished
if (currentEnumeration() == null) {
// No next enum
return false;
}
// If the current enum has more elements, lets go
return currentEnumeration().hasMoreElements();
}
private Enumeration<T> findNextEnumeration(boolean moveCursor) {
return findNextEnumeration(index, moveCursor);
}
private Enumeration<T> findNextEnumeration(int cursor, boolean moveCursor) {
// next place in the array
int next = cursor + 1;
// If the cursor is still in the array
if (next < enumerations.length) {
// If there is something in that place
// AND the enum is not empty
if (enumerations[next] != null && enumerations[next].hasMoreElements()) {
// OK
if (moveCursor) {
index = next;
}
return enumerations[next];
}
// Try next element
return findNextEnumeration(next, moveCursor);
}
// No more elements available
return null;
}
public T nextElement() {
// ask for the next element of the current enum.
if (currentEnumeration() != null) {
return currentEnumeration().nextElement();
}
// no more elements in this Enum
// We must throw a NoSuchElementException
throw new NoSuchElementException("No more elements");
}
private Enumeration<T> currentEnumeration() {
if (enumerations != null) {
if (index < enumerations.length) {
Enumeration<T> e = enumerations[index];
if (e == null || !e.hasMoreElements()) {
// the current enum is null or empty
// we probably want to switch to the next one
e = findNextEnumeration(true);
}
return e;
}
}
return null;
}
}
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