Implement the requested methods Java

6. Given the following Java code fragment, implement the requested methods. You may not introduce any new class level variables. Assume no syntax errors public class BasicTree f private class Node f K key; V value; public Node (K key, V value)[ this.key - key; this. value = value ; Node root; int curSize; k x * Produces the key sequence resulting from a pre-order tree traversal. * Greturn A List of the keys in the tree in pre-order public List preOrderKeys )I // TODO Student Code * Helper function for public recursive methood private List preOrderKeys(Node start)C // TODO Student Code 6. Given the following Java code fragment, implement the requested methods. You may not introduce any new class level variables. Assume no syntax errors public class BasicTree f private class Node f K key; V value; public Node (K key, V value)[ this.key - key; this. value = value ; Node root; int curSize; k x * Produces the key sequence resulting from a pre-order tree traversal. * Greturn A List of the keys in the tree in pre-order public List preOrderKeys )I // TODO Student Code * Helper function for public recursive methood private List preOrderKeys(Node start)C // TODO Student Code