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import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* @since 4.37
* @author Jaroslav Tulach
*/
public class Utils {
/**
* Concatenates the content of two enumerations into one.
* Until the
* end of en1 is reached its elements are being served.
* As soon as the en1 has no more elements, the content
* of en2 is being returned.
*
* @param en1 first enumeration
* @param en2 second enumeration
* @return enumeration
*/
public static Enumeration concat(Enumeration en1, Enumeration en2) {
ArrayList> two = new ArrayList>();
two.add(en1);
two.add(en2);
return new SeqEn(Collections.enumeration(two));
}
}
class SeqEn extends Object implements Enumeration {
/** enumeration of Enumerations */
private Enumeration> en;
/** current enumeration */
private Enumeration current;
/** is {@link #current} up-to-date and has more elements?
* The combination current == null and
* checked == true means there are no more elements
* in this enumeration.
*/
private boolean checked = false;
/** Constructs new enumeration from already existing. The elements
* of en should be also enumerations. The resulting
* enumeration contains elements of such enumerations.
*
* @param en enumeration of Enumerations that should be sequenced
*/
public SeqEn(Enumeration> en) {
this.en = en;
}
/** Ensures that current enumeration is set. If there aren't more
* elements in the Enumerations, sets the field current to null.
*/
private void ensureCurrent() {
while ((current == null) || !current.hasMoreElements()) {
if (en.hasMoreElements()) {
current = en.nextElement();
} else {
// no next valid enumeration
current = null;
return;
}
}
}
/** @return true if we have more elements */
public boolean hasMoreElements() {
if (!checked) {
ensureCurrent();
checked = true;
}
return current != null;
}
/** @return next element
* @exception NoSuchElementException if there is no next element
*/
public T nextElement() {
if (!checked) {
ensureCurrent();
}
if (current != null) {
checked = false;
return current.nextElement();
} else {
checked = true;
throw new java.util.NoSuchElementException();
}
}
}