org.dspace.utils.servicemanager.ProviderStackComparator Maven / Gradle / Ivy
/**
* The contents of this file are subject to the license and copyright
* detailed in the LICENSE and NOTICE files at the root of the source
* tree and available online at
*
* http://www.dspace.org/license/
*/
package org.dspace.utils.servicemanager;
import java.io.Serializable;
import java.util.Comparator;
/**
* A Comparator for provider stacks. This is specially designed for
* sorting a list of ProviderHolders so it will unpack them and then do
* the typical sorting on them while properly handling the null cases.
*
* @author Aaron Zeckoski (azeckoski @ gmail.com)
*/
public final class ProviderStackComparator implements Comparator>, Serializable {
public static final long serialVersionUID = 1l;
public int compare(ProviderHolder ph0, ProviderHolder ph1) {
/* a negative integer, zero, or a positive integer as the first argument
* is less than, equal to, or greater than the second.
*/
int comparison = 0;
Object arg0 = ph0.getProvider();
Object arg1 = ph1.getProvider();
if (arg0 == null && arg1 == null) {
comparison = 0;
} else if (arg0 == null) {
comparison = 1; // null is last
} else if (arg1 == null) {
comparison = -1; // null is last
} else {
comparison = new OrderedServiceComparator().compare(arg0, arg1);
}
return comparison;
}
}