CODEWITHSUNDEEP
java
RBP
RBP

Reputation: 485

How can I remove invalid child nodes in a tree

I have below Tree class with the following attributes and their getters and setters.

public class Tree {
   private String name, address;
   private List<Tree> child; 
}

I am iterating a Tree and comparing the name with a list of valid names. If the name is not valid, I have to remove that specific Tree node from the main Tree. However, I don't know how to implement the remove functionality.

private void validateTree(Tree tree) {
    if (tree.getChild() != null && !tree.getChild().isEmpty()) {
        for(Tree node:tree.getChild()){
            if(list.contains(node.getName())){  // String elements in list
                validateTree(tree); // validate the subtree
            } else {
                // Here I have to remove the child node from the Tree.
            }
        }
    }
}

Upvotes: 0

Views: 346

Answers (2)

algrid
algrid

Reputation: 5954

The safe way to remove an element from a collection is using iterator. In your case it may look like this:

List<Tree> children = tree.getChild();
for (Iterator<Tree> iterator = children.iterator(); iterator.hasNext();) {
    Tree node = iterator.next();
    if (list.contains(node.getName())){  // String elements in list
        validateTree(tree); //OK
    } else {
        iterator.remove();
    }
}

Upvotes: 1

Nick Vanderhoven
Nick Vanderhoven

Reputation: 3093

The easiest way is to add a removeChild() method in your Tree:

public class Tree {

    List<Tree> child;

    public void removeChild(Tree tree) {
        child.remove(tree);
    }
}

In your validation method you can use it:

 if (validNodes.contains(node.getName())) {
    validateTree(tree);
 } else {
    tree.removeChild(node);
 }

However, you should always be very suspicious when you are changing a collection that you are looping over. I would strongly suggest to leave the original Tree as is, and create a second, valid, Tree that only contains the valid nodes.

Upvotes: 2

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