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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.woden.ant;
import java.util.HashMap;
/**
* Provides a completely safe way to generate unique ids for equivalence classes of objects.
* Equivalent objects are assigned the same ids.
* Inequivalent objects are assigned different ids.
* Here equivalance is defined by the equals() method which is used by HashMap.
* Experience has shown that hashCode() occasionally produces the same hash for different objects.
* Note that the objects are permanently stored, so only use this class when serializing
* objects in an XML file.
*
* A count is kept and assigned to each object equivalence class as it is added.
*
* @author Arthur Ryman (ryman@ca.ibm.com, arthur.ryman@gmail.com)
*
*/
public class ObjectIdTable {
private HashMap components = new HashMap();
private int nextId = 1;
/**
* Returns a unique integer for the equivalence class of the object.
*
* @param o An object.
* @return A unique id for the object.
*/
public int id(Object o) {
Integer id = (Integer) components.get(o);
if (id == null) {
id = new Integer(nextId++);
components.put(o, id);
}
return id.intValue();
}
}