String comparison Console App

StringCompareApp.java

// Write a small console application that uses a string comparison function (that you
// will also write) that meets the following prototype:
//
// int MyStrCmp(char *a, char *b) - for C;
// or assume passed String data types - for C# / Java / PHP
//
// Entered or passed strings may be of any length; trap for edge conditions and
// display error messages. Functions cannot make use of or "wrap" any existing API
// calls. Function must return an int that is:
// <0 if string1 is less than string2;
// 0 if string1 is the same as string2; or
// >0 if string1 is greater than string2;
// and display the 2 strings as noted below.
//
// If the return value is <0, then returned strings are inverted, IE abcdef and uvwxyz,
// would be displayed as fedcba and zyxwvu
//
// If the return value is 0, then one string is returned and is made up with the merged
// 2 input strings; IE abcdef and uvwxyz, would be displayed as aubvcwdxeyfz.
//
// If the return value is >0, then one string is returned and is made up with the merged
// 2 input strings; IE abcdef and uvwxyz, would be displayed as zfyexdwcvbua

/**
 * The Class StringCompareApp.
 */
public class StringCompareApp {

  /**
   * The main method.
   * 
   * @param args the arguments
   */
  public static void main(String[] args) {
    String str1 = "abcdef";
    String str2 = "uvwxyz";
    StringCompareApp.run(str1, str2);
  }

  /**
   * The main method.
   * 
   * @param str1 the str1
   * @param str2 the str2
   */
  public static void run(String str1, String str2) {
    int stringCompareVal = stringCompare(str1, str2);
    if (stringCompareVal < 0) {
      System.out.println(reverse(str1) + " and " + reverse(str2));
    } else if (stringCompareVal == 0) {
      System.out.println(merge(str1, str2));
    } else if (stringCompareVal > 0) {
      System.out.println(merge(reverse(str2), reverse(str1)));
    }
  }

  /**
   * String compare method.
   * 
   * @param str1 the str1
   * @param str2 the str2
   * @return the int
   */
  private static int stringCompare(String str1, String str2) {
    int length1 = getStringLength(str1);
    int length2 = getStringLength(str2);
    int returnVal = 0;
    if (length1 < length2)
      returnVal = -1;
    else if (length1 == length2)
      returnVal = 0;
    else if (length1 > length2) returnVal = 1;
    return returnVal;
  }

  /**
   * Finds the string length.
   * 
   * @param str the str
   * @return the string length
   */
  private static int getStringLength(String str) {
    int length = 0;
    try {
      while (true) {
        str.charAt(length);
        length++;
      }
    } catch (StringIndexOutOfBoundsException e) {

    }
    return length;
  }

  /**
   * Reverses the string.
   * 
   * @param str the str
   * @return the string
   */
  private static String reverse(String str) {
    int length = str.length();
    char[] chars = new char[getStringLength(str)];
    int count = 0;
    for (int i = length - 1; i >= 0; i--)
      chars[count++] = str.charAt(i);
    return new String(chars);
  }

  /**
   * Merges the two strings.
   * 
   * @param str1 the str1
   * @param str2 the str2
   * @return the string
   */
  private static String merge(String str1, String str2) {
    int length1 = getStringLength(str1);
    int length2 = getStringLength(str2);
    char[] chars = new char[length1 + length2];
    int max = length1 > length2 ? length1 : length2;
    int count = 0;
    for (int i = 0; i < max; i++) {
      if (i < length1) {
        chars[count] = str1.charAt(i);
        count++;
      }
      if (i < length2) {
        chars[count] = str2.charAt(i);
        count++;
      }
    }
    return new String(chars);
  }
}