1. efficiently implement a stack class using a singly linked list, with no header or tail nodes using java.
2.Write a program that allows the user to enter prefix expressions in a text field. The program reads the expression, evaluates it, and displays the value in a suitable GUI component. Assume that the user enters expressions that use only positive integers and the two operators + and *. your program should internally convert the prefix expression into a binary tree before evaluating it. using java