Code
public static void sortTree(DefaultMutableTreeNode root) {
Enumeration e = root.depthFirstEnumeration();
while (e.hasMoreElements()) {
DefaultMutableTreeNode node = (DefaultMutableTreeNode) e.nextElement();
if (!node.isLeaf()) {
sort2(node); //selection sort
//sort3(node); //JDK 1.6.0: iterative merge sort
//sort3(node); //JDK 1.7.0: TimSort
}
}
}
public static Comparator< DefaultMutableTreeNode> tnc = new Comparator< DefaultMutableTreeNode>() {
@Override public int compare(DefaultMutableTreeNode a, DefaultMutableTreeNode b) {
//Sort the parent and child nodes separately:
if (a.isLeaf() && !b.isLeaf()) {
return 1;
} else if (!a.isLeaf() && b.isLeaf()) {
return -1;
} else {
String sa = a.getUserObject().toString();
String sb = b.getUserObject().toString();
return sa.compareToIgnoreCase(sb);
}
}
};
// JDK 1.8.0
// a lambda expression Comparator
//Comparator< DefaultMutableTreeNode> tnc = Comparator.comparing(DefaultMutableTreeNode::isLeaf)
// .thenComparing(n -> n.getUserObject().toString());
//selection sort
public static void sort2(DefaultMutableTreeNode parent) {
int n = parent.getChildCount();
for (int i = 0; i < n - 1; i++) {
int min = i;
for (int j = i + 1; j < n; j++) {
if (tnc.compare((DefaultMutableTreeNode) parent.getChildAt(min),
(DefaultMutableTreeNode) parent.getChildAt(j)) > 0) {
min = j;
}
}
if (i != min) {
MutableTreeNode a = (MutableTreeNode) parent.getChildAt(i);
MutableTreeNode b = (MutableTreeNode) parent.getChildAt(min);
parent.insert(b, i);
parent.insert(a, min);
}
}
}
public static void sort3(DefaultMutableTreeNode parent) {
int n = parent.getChildCount();
//@SuppressWarnings("unchecked")
//Enumeration< DefaultMutableTreeNode> e = parent.children();
//ArrayList< DefaultMutableTreeNode> children = Collections.list(e);
List< DefaultMutableTreeNode> children = new ArrayList< DefaultMutableTreeNode>(n);
for (int i = 0; i < n; i++) {
children.add((DefaultMutableTreeNode) parent.getChildAt(i));
}
Collections.sort(children, tnc); //iterative merge sort
parent.removeAllChildren();
for (MutableTreeNode node: children) {
parent.add(node);
}
}
References
