1- 1. Implement in JAVA a method in class binary tree of integer to copy the tree in post-order into a singly linked list. 2- 2 Implement in JAVA a recursive method to check that a binary tree of integer numbers is a heap Implement a JAVA method by adding attribute parent to each node in a binary tree, starting from an existing binary tree using in-order method, assign a reference to each parent of any node of the tree. Example the parent of the root is equal to null. 3- 4 Implement in JAVA a method to calculate the sum of all values in a binary tree of integers