Delete Method in a HashMap

I have a code from a trie tree that has insert and search methods, but does not contain a method of removal. I tried to implement but I did not succeed. I would like someone to give you a hint on how to implement it. Using this same code below is it possible to create a function that returns a word from the tree?

public class Trie {

class TrieNode {

    char c;
    HashMap<Character, TrieNode> children = new HashMap<Character, TrieNode>();
    boolean isLeaf;

    public TrieNode() {
    }

    public TrieNode(char c) {
        this.c = c;
    }
}

private TrieNode root;

public Trie() {
    root = new TrieNode();
}

// Insere uma palavra na Trie tree.
public void insert(String word) {
    HashMap<Character, TrieNode> children = root.children;

    for (int i = 0; i < word.length(); i++) {
        char c = word.charAt(i);

        TrieNode t;
        if (children.containsKey(c)) {
            t = children.get(c);
        } else {
            t = new TrieNode(c);
            children.put(c, t);
        }

        children = t.children;

        //set leaf node
        if (i == word.length() - 1) {
            t.isLeaf = true;
        }
    }
}

// Retorna se a palavra estiver na trie tree.
public boolean search(String word) {
    TrieNode t = searchNode(word);

    if (t != null && t.isLeaf) {
        return true;
    } else {
        return false;
    }
}

// Retorna se há alguma palavra na trie
// que começa com o prefixo fornecido.
public boolean startsWith(String prefix) {
    if (searchNode(prefix) == null) {
        return false;
    } else {
        return true;
    }
}

public TrieNode searchNode(String str) {
    Map<Character, TrieNode> children = root.children;
    TrieNode t = null;
    for (int i = 0; i < str.length(); i++) {
        char c = str.charAt(i);
        if (children.containsKey(c)) {
            t = children.get(c);
            children = t.children;
        } else {
            return null;
        }
    }

    return t;
}

}