please help me write this piece of code and explain it in java static BSTNode insert$($BSTNode root, int key$)$

$\{$

$//$ COMPLETE THIS FUNCTION

$//$ YOU CAN USE ANY OF THE OTHER GIVEN, COMPLETED FUNCTIONS HERE

$//$ If the tree is empty

$//$ If the key is already present in the root node

$//$ Otherwise, recur down the tree

$//$ Return unchanged root pointer

$\}$

$//$ function to search in a BST$,$ returns either node with key or null if not found

static BSTNode search$($BSTNode root, int key$)$

$\{$

$//$ COMPLETE THIS FUNCTION

$//$ YOU CAN USE ANY OF THE OTHER GIVEN, COMPLETED FUNCTIONS HERE

$//$ Base Cases: root is null or key is present

$//$ Key is greater than root's key

$//$ Key is smaller than root's key

$\}$

$//$ function to delete node by key in a BST

static BSTNode delNode$($BSTNode root, int x$)\{$

$//$ COMPLETE THIS FUNCTION

$//$ YOU CAN USE ANY OF THE OTHER GIVEN, COMPLETED FUNCTIONS HERE

$//$ If root is null $-$ base case

$//$ If key to be searched is in a subtree

$//$ If root matches with the given key

$//$ Cases when root has no children

$//$ root has only right child

$//$ root has only left child

$//$ When both children are present

$//$ Return unchanged root pointer

$\}$

also is there another way to write them and which method has the best time complexity and why? thank you