Write recursive function using java:

A Full Binary Tree ( every internal node has two children) is used to represent an arithmetic expression using only operators times and add, as illustrated below: Nodes in this structure have the following class variables: boolean internalNode; // true for internal nodes, false for leaf nodes int leafValue; // valid for leaf nodes, ignored for internal nodes char operator; // for internal nodes, { +', '*'}, ignored for leaf nodes Node leftChild; Node rightChild; Write a recursive function, int eval(Node x), that is passed a (possibly null) reference to the root node of an arithmetic expression tree, as described above, and returns the integer result of evaluating the expression