Re-build a Binary Tree from post-order and pre-order traverse

This is a well known problem, if we have two traversals of a binary tree, like post-order and pre-order etc.

we have to build a binary tree from these. Here is an example with post-order and pre-order case.

import java.util.Arrays;
import java.util.List;

public class ReConstructBTree {

/**
* @param args
*/
public static void main(String[] args) {

String[] pre = "I Q J H L E M V O T S B R G Y Z K C A & F P N U D W X".split("\\s");
String[] post = "H E M L J V Q S G Y R Z B T C P U D N F W & X A K O I".split("\\s");

List preList = Arrays.asList(pre);
List postList = Arrays.asList(post);

BTree tree = reBuildTree(preList, postList);

tree.inOrder(tree); //print in-order
System.out.println();
tree.postOrder(tree);//print post order to re-check
System.out.println();
tree.preOrder(tree);//print pre order to re-check
}

private static BTree reBuildTree(List preList, List postList) {
BTree tree = null;

if(preList.size() != 0 && postList.size() != 0) {
tree = new BTree();
String val = preList.get(0);
tree.val = val;

if(preList.size() > 1 && postList.size() > 1) {
int postOrderPos = postList.indexOf(preList.get(1));
int preOrderPos = preList.indexOf(postList.get(postList.size()-2));

//find the two sub set of the list from pre-order
List leftPreOrder = preList.subList(1, preOrderPos);
List rightPreOrder = preList.subList(preOrderPos, preList.size());

//find the two sub set of the list from post-order
List leftPostOrder = postList.subList(0, postOrderPos+1);
List rightPostOrder = postList.subList(postOrderPos+1, postList.size()-1);

tree.left = reBuildTree(leftPreOrder, leftPostOrder);
tree.right = reBuildTree(rightPreOrder, rightPostOrder);
}
}

return tree;
}

static class BTree {
String val;
BTree left;
BTree right;

void inOrder(BTree tree) {
if(tree.left != null)
inOrder(tree.left);
System.out.print(tree.val+" ");
if(tree.right != null)
inOrder(tree.right);
}

void preOrder(BTree tree) {
System.out.print(tree.val+" ");
if(tree.left != null)
preOrder(tree.left);
if(tree.right != null)
preOrder(tree.right);
}

void postOrder(BTree tree) {
if(tree.left != null)
postOrder(tree.left);
if(tree.right != null)
postOrder(tree.right);
System.out.print(tree.val+" ");
}

}
}