Question

Lab 12 - If y cn rd ths, y cn b a gd prgrmmr.

In this lab, you will explore String manipulation by removing characters from Strings. Even with many characters removed, it is still possible too get the meaning. While this isn’t exactly lossy compression, it does show you that even with information removed, you can still understand what you are looking at even if the quality is not the same.

Step 0: Constant

Create a public static final String called VOWELS at the topic of your class. Initialize it to “aeiouAEIOU”. You will use this later.

Step 1: lettersAndWhitespaceOnly(String)

For this method, you will take in a message, and keep only letters and whitespace. Everything else (numbers, punctuation, etc) will be removed. So for example

String value = lettersAndWhitespaceOnly("The number 42 is a number that is popular due to Hitchhikers Guide to the Galaxy.")

would set value equal to

"The number  is a number that is popular due to Hitchhikers Guide to the Galaxy"

While

String value = lettersAndWhitespaceOnly("!@!(*&(*&)!(!x*@)9191828101")

would set the value equal to

"x"

Writing lettersAndWhitespaceOnly

For this method, we already gave you the method stub, so you will only need to write a loop.

To help the loop conditions are from 0 to the length of the String, so as follows:

for(int i = 0; i < message.length(); i++) {
   // do something here
}

You will then want to check the character at that location, to see if it is a letter or whitespace and if it is, add it too the return string.

Some helpful methods are:

• .charAt(index)
• Character.isWhitespace(char)
• Character.isLetter(char)
• Zybooks Chapter on Character

Step 2: removeWhiteSpace(String)

For this method, you will take in a message, and remove all whitespace from the message. Imeanwecanallreadwithoutwhitespace - ok, let’s try that again. We can all read without whitespace.

In either case, this is a nice warm up, that will help for the other methods.

Writing removeWhiteSpace(String)

You will start off with a very similar loop as the last method, and instead of looking for whitespace and letters - you will only need to look for whitespace. The difference is:

• If you find whitespce - DON’T Add it to the return String
• everything else, add it!

Step 3: hasCharacter(char, String)

This is your first helper method for the lossy compression, and will make it easier to work getting this one right. The goal is to take a character, and check to see if that character is in a group of characters. For example, is x in the AeiOu? You know that it isn’t, so the method should return false.

Start thinking of ways that you can solve this problem, and then you can start writing after you get an idea.

Writing hasCharacter(char, String)

First, you will need to write the method signature. If you look at the comments there is a good spot to add it. The hasCharacter method is a public static method that returns a boolean value. It needs to take in a character and String as parameters in that order. You can call them what you want, but I called my character x and my string group (ok, maybe not the best names for each…)

Second, you will want to go through the String to see if the character from the parameter exists in the String. You can do this either with a loop and charAt, or you can do it with .contains (group.contains()). I found using the built in String method to be easier.

Step 4: stringShortener(String, String)

Next, you will want to find the comments just above the main method - the ones for the 2 parameter stringShortner method. You will work on this one first, and then go back up to the one parameter version.

This method is your lossy compression! (finally!). The goal is to write a method that takes in a String, and removes all characters that show up in the second string passed in. It will keep a character if it is the start of a word (i.e. following a space)

For example

You can be a good programmer, if you can read this.

would return if VOWELS was used as the list of characters to remove

Y cn b a gd prgrmmr, if y cn rd ths.

Writing stringShortener(String, String)

• First write the method signature. It is a public static method that returns a String, and takes in two String parameters - a message and a group of characters to remove as a String - in that order.

• You will then need to create an empty String like was created in the first two methods you wrote. This is the same String you will return. Hint: I would compile here, just to make sure it is compiling.

• Next, loop through the first String (your message), and check to see if the character at position i is in your group of characters to remove. Hint use hasCharacter! If it is NOT in that group, OR if the character before your current location is a space (the tricky part), then you add it to the the rtn string.

It may be easier to ignore the ‘space’ rule, and get it working. You will then want to try it again, figuring out the space condition. Remember, prototype and repeat tirelessly.

Step 5: stringShortener(String)

Now go up into your code that talks about a stringShortener that only takes in 1 parameter. This is your chance to practice method overloading.

The goal is to assume the default group to remove is VOWELS, as really, who needs vowels when you are writing?

Writing stringShortener(String)

• First write the method signature. It is the same as the other stringShortener, but only has a String messafe as a parameter

• call stringShortener(String, String) passing in message and VOWELS as your parameter. Return the value returned from that method!

PROVIDED CODE:

public class LossyString {

// ADD CONSTANT HERE

/**
* Keeps both letters and whitespace only. Everything else is removed
* @param message the string that you want to keep letters and whitespace only
* @return the converted string
*/
public static String lettersAndWhitespaceOnly(String message) {
String rtn = "";

// STUDENT CODE HERE
return rtn;
}

/**
* Removes all whitespace from a string
* @param message the string you wish to have space removed
* @return the new string with whitespace removed
*/
public static String removeWhiteSpace(String message) {
String rtn = "";
// STUDENT CODE HERE

return rtn;
}

/**
* hasCharacter(char, String) Helper method for two-parameter {@link #stringShortener(String, String)}.
* This method determines if one character from the source String is included in the characters
* of the String representing all characters to remove. If so, return true.
*
* @param x A character representing one character from the source String.
* @param group A String representing all characters to remove.
* @return A boolean.
*/
//STUDENT CODE HERE

/**
* stringShortener(String) Remove vowels from a string.
* It will use the default {@link #VOWELS} constant variable for the second parameter, as often
* VOWELS removed from words are easy for our mind to replace.
* @param stringToCheck A String representing the String to check for matching characters in.
* @return A new String with matching characters of source String removed.
*/
//STUDENT CODE HERE

/**
* stringShortener(String, String) Remove all characters listed in one String from another String.
* This method does not ignore case and does not remove a character if it is the
* 'start' of a word after a space.
* i.e.
* <pre>
* You can be a good programmer, if you can read this.
*
* Y cn b a gd prgrmmr, if y cn rd ths.
* </pre>
* @param stringToCheck A String representing the String to check for matching characters.
* @param charsToRemove A String representing the String of characters to remove.
* @return A String with characters removed.
* @see #hasCharacter(char, String)
*/
// STUDENT CODE HERE

public static void main(String[] args) {

}

}

Answer 1

CODE:

public class LossyString
{
   //we define a static final string variable which stores the list of all the vowels
   public static final String Vowels = "aeiouAEIOU";
   //this method only keeps letters and white spaces, removes rest of them
   public static String lettersAndWhitespaceOnly(String message)
   {
       //define a variable "rtn" to store string to be returned
       String rtn = "";
       //this loops traverse through all the characters in the string
       for(int i=0;i<message.length();i++)
       {
           //checks if the i-th characters is in range (a,z) or (A,Z) or whitespace
           //if it is then we add that to return string
           if((message.charAt(i)>='a' && message.charAt(i)<='z') ||
           (message.charAt(i)>='A' && message.charAt(i)<='Z') ||
           message.charAt(i) == ' ')
           {
               rtn+=message.charAt(i);
           }
       }
       //return the "rtn" string
       return rtn;
   }
   //this function takes in a string and returns a string after removing all the whitespaces from it
   public static String removeWhiteSpace(String message)
   {
       //define a variable "rtn" to store string to be returned
       String rtn = "";
       //this loops traverse through all the characters in the string
       for(int i=0;i<message.length();i++)
           //it checks, if element at i-t position is white space or not
           if(message.charAt(i)!= ' ')
               //if not then we add that character to the "rtn" string
               rtn += message.charAt(i);
       //return the "rtn" string
       return rtn;
   }
   //this function takes a character and a string, returns true if character is in string, othrewise false
   public static boolean hasCharacter(char x, String group)
   {
       //we define a boolean variable
       //initialize it with "false", which represents character is not present in the string
       boolean b = false;
       //this loop traverse through all the character in the string to be matched
       for(int i=0;i<group.length();i++)
           //if character is in the string then we make "b" to true, which represents character is in string
           if(x == group.charAt(i))
               b = true;
       //return the boolean value
       return b;
   }
   //this function takes in a string and removes all the vowels from them
   public static String stringShortner(String stringToCheck)
   {
       //define a variable "rtn" to store string to be returned
       String rtn = "";
       //this loops traverse through all the characters in the string
       for(int i=0;i<stringToCheck.length();i++)
           //we call "hasCharacter" function and pass i-th element of string and vowels string
           //if fnction returns false then we add the i-th element to return string else we dont
           if(hasCharacter(stringToCheck.charAt(i), Vowels) == false)
               rtn += stringToCheck.charAt(i);
       //return the "rtn" string
       return rtn;
   }
   //this function takes two string, and removes all the letters of second string from first string
   public static String stringShortner(String stringToCheck, String charsToRemove)
   {
       //define a variable "rtn" to store string to be returned
       String rtn = Character.toString(stringToCheck.charAt(0));
       //this loops traverse through all the characters in the string
       for(int i=1;i<stringToCheck.length();i++)
       {
           //we check for the i-th character with help of "hasCharacter" function, if i-th element is in charsToRemove string
           //if not then we add it to string
           //or we add it if the character is preceded by a white space
           if(hasCharacter(stringToCheck.charAt(i), charsToRemove) == false || stringToCheck.charAt(i-1) == ' ')
               rtn += stringToCheck.charAt(i);          
       }
       //return the "rtn" string
       return rtn;
   }
   public static void main(String[] args)
   {
       //define a string to test letterAndWhitespaceOnly function
       String strs = "!@!(*&(*&)!(!x*@)9191828101";
       //define a string to test rest of the functions
       String strs1 = "You can be a good programmer, if you can read this";
       //tests all the function, one-by-one and print its output
       System.out.println(lettersAndWhitespaceOnly(strs));  
       System.out.println(removeWhiteSpace(strs1));
       System.out.println(stringShortner(strs1));
       System.out.println(stringShortner(strs1, Vowels));
   }
}

OUTPUT:

x
Youcanbeagoodprogrammer,ifyoucanreadthis
Y cn b gd prgrmmr, f y cn rd ths
Y cn b a gd prgrmmr, if y cn rd ths

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