de.schlichtherle.truezip.util.JointEnumeration Maven / Gradle / Ivy
/*
* Copyright (C) 2005-2015 Schlichtherle IT Services.
* All rights reserved. Use is subject to license terms.
*/
package de.schlichtherle.truezip.util;
import java.util.Enumeration;
import java.util.NoSuchElementException;
import javax.annotation.concurrent.NotThreadSafe;
/**
* Concatenates two enumerations.
*
* @author Christian Schlichtherle
*/
@NotThreadSafe
public final class JointEnumeration implements Enumeration {
private Enumeration e1;
private final Enumeration e2;
public JointEnumeration(
final Enumeration e1,
final Enumeration e2) {
this.e1 = e1;
this.e2 = e2;
}
@Override
public boolean hasMoreElements() {
return e1.hasMoreElements()
|| (e1 != e2 && (e1 = e2).hasMoreElements());
}
@Override
public E nextElement() {
try {
return e1.nextElement();
} catch (NoSuchElementException ex) {
if (e1 == e2)
throw ex;
return (e1 = e2).nextElement();
}
}
}