A tree structure that maps inheritance hierarchies of classes
/*
* The contents of this file are subject to the Sapient Public License
* Version 1.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
* http://carbon.sf.net/License.html.
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for
* the specific language governing rights and limitations under the License.
*
* The Original Code is The Carbon Component Framework.
*
* The Initial Developer of the Original Code is Sapient Corporation
*
* Copyright (C) 2003 Sapient Corporation. All Rights Reserved.
*/
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* <p>This class creates a tree structure that maps inheritance hierarchies of
* classes. A developer can place any number of classes into this object and
* retrieve the closest super class or the class itself.</p>
*
*
* Copyright 2001 Sapient
* @since EJFW 2.7
* @author Greg Hinkle, January 2001
* @version $Revision: 1.4 $($Author: dvoet $ / $Date: 2003/05/05 21:21:23 $)
*/
public class ClassTree {
protected ClassTreeNode bottom;
/**
* Constructs a ClassTree that represents all classes and interfaces that
* are generalizations of the provided class. This ends up with a tree
* structure of the inheritance hierarchy for that provided class all the
* way up to java.lang.Object.
* @param specificClass The class to build the tree for.
*/
public ClassTree(Class specificClass) {
this.bottom = ClassTreeNode.buildNode(specificClass);
}
public ClassTreeNode getBottom() {
return this.bottom;
}
/**
* Constructs an ordered list starting at the highest (most general) class
* in the tree and moving down the tree, ensuring no generalization comes
* after one of its specializations.
* @return a list ordered as above
*/
public List getOrderedList() {
List list = new ArrayList();
list.add(getBottom());
buildList(getBottom(),list);
Collections.sort(list);
// Refactor list into a list of classes from a list of ClassTreeNodes
for (int i = 0; i < list.size(); i++) {
ClassTreeNode node = (ClassTreeNode) list.get(i);
list.set(i,node.getObjectClass());
}
// Reverse the list so that the top class in the hierarchy comes first
Collections.reverse(list);
return list;
}
/**
* <p>Build breadth first in order to maintain sudo ordering as per
* class declarations (i.e. if A implements B, C... B is closer in the
* chain to A than C is, because B comes first in the implements clause.</p>
*
* <p>Note that the list coming out here is preordered, but not natural
* ordered. (i.e. some classes are out of order in relation to classes
* they have direct relationships with. This is later fixed by a sort
* on the list by natural ordering. Collecitons.sort, does preserve
* the preordering for nodes that have no relationship.</p>
*
* @param node the node to be browsed.
* @param output this list is altered to add the contents as they are
* browsed in breadth-first order. Start with a list containing only
* the bottom node.
*/
private void buildList(ClassTreeNode node, List output) {
for (int i = 0; i < node.getParents().size(); i++) {
ClassTreeNode parent = (ClassTreeNode) node.getParents().get(i);
if (!output.contains(parent)) {
output.add(parent);
}
}
List parents = node.getParents();
for (int i = 0; i < parents.size(); i++) {
ClassTreeNode parent = (ClassTreeNode) parents.get(i);
buildList(parent, output);
}
}
/**
* <p>Inner class representing each node in the tree. Holds references to the
* nodes children, parent and provides the Comparable interface for sorting
* by inheritance hierarchy.</p>
*/
public static class ClassTreeNode implements Comparable {
/** The class of this node */
protected Class objectClass;
/** The map of children classes to their class names */
protected List children;
/** A reference to the parent node of this node */
protected List parents;
/**
* <p>Constructs a ClassTreeNode with the given Class.</p>
*
* @param objectClass the Class of the node
*/
public ClassTreeNode(Class objectClass) {
this.children = new ArrayList();
this.objectClass = objectClass;
this.parents = new ArrayList();
}
public static ClassTreeNode buildNode(Class objectClass) {
Map allNodes = new HashMap();
return buildNode(objectClass, allNodes);
}
protected static ClassTreeNode buildNode(Class objectClass, Map allNodes) {
ClassTreeNode node;
if (allNodes.containsKey(objectClass)) {
node = (ClassTreeNode) allNodes.get(objectClass);
} else {
node = new ClassTreeNode(objectClass);
allNodes.put(objectClass, node);
}
// Add the implemented interfaces...
Class[] superInterfaces = objectClass.getInterfaces();
for (int i = 0; i < superInterfaces.length; i++) {
Class superInterface = superInterfaces[i];
ClassTreeNode parent = buildNode(superInterface);
node.addParent(parent);
}
// Add the superclass after the interfaces...
Class superClass = objectClass.getSuperclass();
if (superClass != null) {
ClassTreeNode parent = buildNode(superClass);
node.addParent(parent);
}
return node;
}
public List getParents() {
return this.parents;
}
public void addParent(ClassTreeNode node) {
this.parents.add(node);
node.addChild(this);
}
public boolean removeChild(ClassTreeNode node) {
return this.children.remove(node);
}
public void addChild(ClassTreeNode node) {
this.children.add(node);
}
public List getChildren() {
return this.children;
}
public boolean equals(Object obj) {
return ((ClassTreeNode)obj).getObjectClass().equals(this.objectClass);
}
public Class getObjectClass() {
return this.objectClass;
}
public String getClassName() {
return this.objectClass.getName();
}
public int hashCode() {
return this.objectClass.hashCode();
}
/**
* <p>Compares one class to another class by their inheritance tree.</p>
*
* @return an integer representing the comparison results as follows:<br>
* 2 if this is a subclass of past in object<br>
* -2 if this is a superclass of past in object<br>
* 0 if they are not related (and in relation to sorting, equal)<br>
* 0 if they are the same<br>
*/
public int compareTo(Object obj) {
Class objClass = ((ClassTreeNode)obj).getObjectClass();
if (objClass.equals(this.objectClass)) {
return 0;
} else if (this.objectClass.isAssignableFrom(objClass)) {
return 2;
} else if (objClass.isAssignableFrom(this.objectClass)) {
return -2;
} else {
return 0;
}
}
} // End of ClassTree$ClassTreeNode
}
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