Reverse a String using Stack Data Structure in Java

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In this article, we will discuss how to reverse a string using stack operations.

Reverse a String using Stack Data Structure

This program uses stack operations to reverse a word (string). First, we push each character to the stack, then we will pop each char from the stack.
public class ReverseStringUsingStackDS {

    public String reverseWord(String word) {

        StringBuilder stringBuilder = new StringBuilder();
        int size = word.length();
        StackArray stack = new StackArray(size);
        for(char c : word.toCharArray()){
            stack.push(c);
        }
        while (!stack.isEmpty()) {
            stringBuilder.append(stack.pop());
        }
        return stringBuilder.toString();
    }

    public static void main(String a[]) {
        ReverseStringUsingStackDS mwr = new ReverseStringUsingStackDS();
        System.out.println("javaguides == " + mwr.reverseWord("javaguides"));
        System.out.println("Java == " + mwr.reverseWord("Java"));
        System.out.println("program == " + mwr.reverseWord("program"));
    }

    class StackArray {
        private int stackSize;
        private char[] stackArr;
        private int top;

      /**
      * constructor to create stack with size
      * @param size
      */
     public StackArray(int size) {
         this.stackSize = size;
         this.stackArr = new char[stackSize];
         this.top = -1;
     }

     /**
      * This method adds new entry to the top of the stack
      * 
      * @param entry
      * @throws Exception
      */
      public void push(char entry) {
          this.stackArr[++top] = entry;
      }

     /**
      * This method removes an entry from the top of the stack.
      * 
      * @return
      * @throws Exception
      */
     public char pop() {
         char entry = this.stackArr[top--];
         return entry;
     }

     /**
      * This method returns top of the stack without removing it.
      * 
      * @return
      */
     public char peek() {
         return stackArr[top];
     }

     /**
      * This method returns true if the stack is empty
      * 
      * @return
      */
     public boolean isEmpty() {
         return (top == -1);
     }

     /**
      * This method returns true if the stack is full
      * 
      * @return
      */
     public boolean isFull() {
         return (top == stackSize - 1);
     }
   }
}
Output
javaguides == sediugavaj
Java == avaJ
program == margorp

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