Java Examples - String reversal using stack


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Problem Description

How to reverse a string using stack ?

Solution

Following example shows how to reverse a string using stack with the help of user defined method StringReverserThroughStack().

import java.io.IOException;

public class StringReverserThroughStack {
   private String input; 
   private String output;
   public StringReverserThroughStack(String in) {
      input = in;
   }
   public String doRev() {
      int stackSize = input.length(); 
      Stack theStack = new Stack(stackSize); 
      
      for (int i = 0; i < input.length(); i++) {
         char ch = input.charAt(i); 
         theStack.push(ch); 
      }
      output = "";
      while (!theStack.isEmpty()) {
         char ch = theStack.pop(); 
         output = output + ch; 
      }
      return output;
   }
   public static void main(String[] args) throws IOException {
      String input = "Java Source and Support";
      String output;
      StringReverserThroughStack theReverser = 
      new StringReverserThroughStack(input);
      output = theReverser.doRev();
      System.out.println("Reversed: " + output);
   }
   class Stack {
      private int maxSize;
      private char[] stackArray;
      private int top;
      
      public Stack(int max) {
         maxSize = max;
         stackArray = new char[maxSize];
         top = -1;
      }
      public void push(char j) {
         stackArray[++top] = j;
      }
      public char pop() {
         return stackArray[top--];
      }
      public char peek() {
         return stackArray[top];
      }
      public boolean isEmpty() {
         return (top == -1);
      }
   }
}

Result

The above code sample will produce the following result.

JavaStringReversal
Reversed:lasreveRgnirtSavaJ

The following is an example to reverse a string using stack.

import java.util.Scanner;

class Stack {
   private int maxSize;
   private char[] stackArray;
   private int top;
   
   public Stack(int s) {
      maxSize = s;
      stackArray = new char[maxSize];
      top = -1; 
   } 
   public void push(char j) {
      stackArray[++top] = j;
   } 
   public char pop() {
      return stackArray[top--];
   } 
   public char peek() {
      return stackArray[top];
   } 
   public boolean isEmpty() { 
      return (top == -1);
   } 
   public boolean isFull() {
      return (top == maxSize - 1);
   }
}
public class Demo {
   public static void main(String[] args) {
      System.out.println("Enter a sentence: ");
      Scanner scan = new Scanner(System.in);
      String input = scan.nextLine();
      int stackSize = input.length();
      Stack theStack = new Stack(stackSize);
      
      for (int j = 0; j < input.length(); j++) {
         char ch = input.charAt(j);
         theStack.push(ch);
      } 
      while (!theStack.isEmpty()) {
         char ch = theStack.pop();
         System.out.println(ch);
      } 
   }
}

The above code sample will produce the following result.

Enter a sentence: 
sai
i
a
s

java_data_structure.htm

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