Beginning Java Data Structures and Algorithms

Reversing a String

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();} 

Snippet 2.23: ...