LinkedList.java

class LinkedList {
	private class Node {
		public char data;
		public Node next;
		
		Node(char d, Node n) {
			data = d;
			next = n;
		}
	}
	
	Node head = null;
	int size = 0;
	
	public void add(char d) {
		if(head == null) {
			head = new Node(d, null);
		} else {
			Node curr;
			for(curr = head; curr.next != null; curr = curr.next);
			curr.next = new Node(d, null);
		}
		
		size++;
	}
	
	public void clear() {
		size = 0;
		head = null;
	}
	
	public String toString() {
		String buf = "";
		
		for(Node curr = head; curr != null; curr = curr.next) {
			buf = buf + curr.data;
		}
		
		return buf;
	}
}

LinkedListTester.java

public class LinkedListTester {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		LinkedList test = new LinkedList();
		
		test.add('d');
		test.add('a');
		test.add('m');
		test.add('n');
		
		System.out.printf("Size: %d, Contents: %s", test.size, test.toString());
	}

}

MutableString.java

public class MutableString implements Comparable<MutableString> {
	LinkedList list = new LinkedList();
	
	public MutableString(String data) {
		for(char c : data.toCharArray()) {
			list.add(c);
		}
	}
	
	private void setString(String data) {
		list.clear();
		
		for(char c : data.toCharArray()) {
			list.add(c);
		}
	}
	
	public char chatAt(int i) {
		return list.toString().charAt(i);
	}
	
	public void set(int i, char data) throws MutableStringIndexOutOfBoundsException {
		char[] variance = list.toString().toCharArray();
		
		try {
			variance[i] = data;
		} catch (Exception e) {
			throw new MutableStringIndexOutOfBoundsException();
		}
		
		setString(new String(variance));
	}
	
	public void toUpper() {
		setString(list.toString().toUpperCase());
	}
	
	public void toLower() {
		setString(list.toString().toLowerCase());
	}
	
	public MutableString substring (int start, int finish) {
		return new MutableString(list.toString().substring(start, finish));
	}
	
	public int length() {
		return list.size;
	}
	
	public char[] toCharArray() {
		return list.toString().toCharArray();
	}
	
	public String toString() {
		return list.toString();
	}

	public int compareTo(MutableString arg0) {
		return list.toString().compareTo(arg0.toString());
	}
	
	public String toReverseString() {
		return "";
	}
	
	public void remove(int i) {
		String finals = list.toString().substring(0, i) + 
						list.toString().substring(i+1, list.size);
		
		setString(finals);
	}
	
	public Character remove(char c) {
		LinkedList temp = new LinkedList();
		
		char r = '\0';
		boolean removed = false;
		
		for (char d : list.toString().toCharArray()) {
			if(!removed && d == c) {
				r = d;
				removed = true;
				continue;
			}
			
			temp.add(d);
		}
		
		list = temp;
		
		return r;
	}
	
}

MutableStringTester.java

public class MutableStringTester {

	/**
	 * @param args
	 * @throws MutableStringIndexOutOfBoundsException 
	 */
	public static void main(String[] args) throws MutableStringIndexOutOfBoundsException {
		// TODO Auto-generated method stub
		MutableString test = new MutableString("This is a taco.");
		
		System.out.println(test.chatAt(3));
		test.set(4, '2');
		System.out.println(test.toString());
		for (char c : test.toCharArray()) {
			System.out.print(c + "\t");
		}
		System.out.println();
		
		test.toUpper();
		System.out.println(test.toString());
		test.toLower();
		System.out.println(test.toString());
		MutableString sub = test.substring(4, 8);
		System.out.println(sub.toString());
		
		test.remove('t');
		System.out.println(test.toString());
		
		test.remove(1);
		System.out.println(test.toString());
		
		
	}

}