Question

USING JAVA

Consider the following methods:
StringBuilder has a method append(). If we run:
StringBuilder s = new StringBuilder();
s.append("abc");
The text in the StringBuilder is now "abc"
Character has static methods toUpperCase() and toLowerCase(), which convert characters to upper or lower case. If we run Character x = Character.toUpperCase('c');, x is 'C'.
Character also has a static isAlphabetic() method, which returns true if a character is an alphabetic character, otherwise returns false.
You will also need String's charAt() method, which returns the character at a given index in the String. For example, "Godzilla".charAt(1) returns 'o'.

Write an application as follows:
public static String getNonAlpha() takes a String as parameter, builds a StringBuilder consisting of only the nonalphabetic characters in the String, and returns a String based on the StringBuilder (eg, sb.toString())
public static String getUpper() takes a String, builds a StringBuilder of the upper case versions of all the alphabetic characters in the String, and returns a String based on the StringBuilder.
Write JUnit tests to verify that the above methods are correct

Answer 1

Here is the completed code for this problem including JUnit tests. Comments are included, go through it, learn how things work and let me know if you have any doubts or if you need anything to change. If you are satisfied with the solution, please rate the answer. Thanks

// StringBufferMethods.java

import static org.junit.Assert.*;

import org.junit.Test;

public class StringBufferMethods {

      // returns a String containing all non-alphabetic characters in text

      public static String getNonAlpha(String text) {

            // creating a StringBuffer

            StringBuffer buffer = new StringBuffer();

            // looping through each character

            for (int i = 0; i < text.length(); i++) {

                  // if current character is not a letter, appending to buffer

                  if (!Character.isLetter(text.charAt(i))) {

                        buffer.append(text.charAt(i));

                  }

            }

            return buffer.toString();

      }

      public static String getUpper(String text) {

            // creating a StringBuffer

            StringBuffer buffer = new StringBuffer();

            // looping through each character

            for (int i = 0; i < text.length(); i++) {

                  // if current character is a letter, converting to upper case and

                  // appending to buffer

                  if (Character.isLetter(text.charAt(i))) {

                        buffer.append(Character.toUpperCase(text.charAt(i)));

                  }// note: this method ignores all other characters

            }

            return buffer.toString();

      }

      // JUnit test methods to test the above two methods

      @Test

      public void testGetNonAlpha() {

            // testing normal case

            assertEquals(getNonAlpha("abcd#$.ef12XX"), "#$.12");

            // testing a String that has no non-alphabetic characters

            assertEquals(getNonAlpha("abcd"), "");

            // testing a String that has only non-alphabetic characters

            assertEquals(getNonAlpha("..@@@##"), "..@@@##");

            // testing an empty String

            assertEquals(getNonAlpha(""), "");

      }

      @Test

      public void testGetUpper() {

            // testing normal case

            assertEquals(getUpper("ab.12@Dce"), "ABDCE");

            // testing a String containing only lower case characters

            assertEquals(getUpper("xyz"), "XYZ");

            // testing a String containing only numbers

            assertEquals(getUpper("1234"), "");

            // testing a String containing only upper case characters

            assertEquals(getUpper("ABC"), "ABC");

            // testing an empty String

            assertEquals(getUpper(""), "");

      }

}