We need to make use of a stack data structure for reversing a string.

Follow these steps:

1. To reverse the string, push of each character of the input string and then pop everything out, one at a time, building a reversed string. The method signature can be as follows:

public String reverse(String str) 

2. The following code shows how a string can be reversed using the stack data structure:

public String reverse(String str) {
  StringBuilder result = new StringBuilder();
  Stack<Character> stack = new Stack<>();
  for (char c : str.toCharArray())
  stack.push(c);
  Optional<Character> optChar = stack.pop();
  while (optChar.isPresent()) {
    result.append(optChar.get());
    optChar = stack.pop();
  }
  return result.toString();
} 

Stack data structures are extensively used in computer science for many algorithms. In this section, we have seen how to implement them in a dynamic fashion using linked lists. In the next section, we shall see how to model stacks and queue in a static manner using arrays.