Construct Binary Tree from Inorder and Postorder Traversal

public class Solution {
    public TreeNode buildTree(int[] inorder, int[] postorder) {
        if(inorder == null || inorder.length == 0)  return null;
        if(inorder.length == 1) return new TreeNode(inorder[0]);
        int len = postorder.length;
        int target = postorder[len-1];
        int index = getIndex(inorder, target);
        TreeNode root = new TreeNode(target);
        root.left = buildTree(Arrays.copyOfRange(inorder,0,index),Arrays.copyOfRange(postorder,0,index));
        root.right = buildTree(Arrays.copyOfRange(inorder, index+1, len),Arrays.copyOfRange(postorder, index, len-1));
        return root;
    }
    public int getIndex(int[] inorder, int target)
    {
        for(int i = 0; i < inorder.length; i++)
        {
            if(inorder[i] == target)
                return i;
        }
        return -1;
    }
}