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) {
// ...
}
};
// 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<>(n);
for (int i = 0; i < n; i++) {
children.add((DefaultMutableTreeNode) parent.getChildAt(i));
}
Collections.sort(children, tnc); // using Arrays.sort(...)
parent.removeAllChildren();
for (MutableTreeNode node: children) {
parent.add(node);
}
}
References
