Question

Use stacks to implement a program in JAVA that will prompt the use to type a word, then print that word in reverse order of letters, then ask the user for another word, and so on. The program should terminate when the user enters "STOP" in upper case.

Your deliverables shall include:

• class and method specifications;
• class and method definitions;
• at test class with at least two @test methods.

Answer 1

Step-1)Define a method reverseWord . Iterate on the given word and push the letters in the word in a stack.

Step-2)Continue popping letters from stack till the stack is not empty and append those letters in a StringBuilder.

Step-3)Convert StringBuilder to String and return it.

To write testcases create a test class => In the test class create a method test_reverseWord()

Create a instance of ReverseWord Class and call reverseWord method using it and pass the word you wish to reverse as an argument to it.

Finally use assertEquals to match the response with expected result.

import java.util.Scanner;
import java.util.Stack;

public class Reverseword {

    public Reverseword(){

    }

    public static String reverseWord(String word){
        Stack<Character> stack = new Stack<Character>();

        for(int i=0;i<word.length();i++){
            stack.push(word.charAt(i));
        }

        StringBuilder result = new StringBuilder();
        while(!stack.empty()){
            result.append(stack.pop());
        }

        return result.toString();

    }

    public static void main(String []args){
        Scanner sc = new Scanner(System.in);
        while(true) {
            System.out.println("enter a word to get reversed : ");
            String word = sc.next();
            if (word.equals("STOP"))
                System.exit(0);
            else {
                System.out.println("Reversed word is : " + reverseWord(word));
            }
        }
    }
}

Testcases:

import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;

public class ReversewordTest {

    public Reverseword reverseword;

    @Before
    public void setUp() throws Exception {
      reverseword = new Reverseword();
    }

    @Test
    public void test_reverseWord() {
        String value1 = this.reverseword.reverseWord("java");
        Assert.assertEquals("avaj", value1);

        String value2 = this.reverseword.reverseWord("HomeworkLib");
        Assert.assertEquals("ggehc", value2);
    }
}

If you have any doubt in understanding the code or running the code , just comment on the answer and i would be happy to help you out.