I'm having trouble with "this" and method dependence

Question

For my Data Structures course, we have to create a simple Word Processor. The constructor contains two stacks, left and right. The way the class populates the strings is pretty straight forward. Any text to the left of the cursor gets pushed onto the left stack and any text to the right of the cursor gets pushed onto the right stack (in reverse order). For example, the phrase "hello" with the cursor between the l's, would push h, then e, then l onto the left stack. o then l is pushed onto the right stack. Follow me so far?
Next, we have to implement several methods, such as moveLeft, moveRight, delete, insert, and moveToStart. There is also a toString() method which prints the two stacks as a String. The way I have my toString() method mapped out, is first to call the moveToStart() method. This method then pops all values from the left stack and pushes them onto the right stack (left: empty, right: h-e-l-l-o). So now, I simply pop each value from the right stack and store the values in a char[] array. The array is then returned as a String.
This data structure converts the stacks to a String fine, the only problem is preserving the original stacks. So I tried to copy the value of "this," which should correlate to the EditableString es2 (declared in main), to a temp EditableString, tempEs. I then call moveToStart on tempEs, and pop values from tempEs.right. This is all in hopes to preserve the original es2. However, as you could see from the output at the bottom is that toString() modifies es2. If it didn't, "Hello, how are you" would have printed twice. Instead, an empty string is printed.
There is obviously something wrong with my moveToStart(). Any suggestions? I apologize for not providing any comments in the code, it's just that I tried to save space. If any further explanation is necessary, don't hesitate to ask. Thanks.
public class EditableString {
private Stack left;
private Stack right;
private JavaStack l = new JavaStack();
private JavaStack r = new JavaStack();
private char[] text;
private static String cursor = new String("|");
private EditableString tempEs;
private Character characterObject;
private char test1;
public EditableString() {
left = new JavaStack();
right = new JavaStack();
public EditableString(String left, String right) {
new EditableString();
for (int i=0; i < left.length(); i++) {
characterObject = new Character(left.charAt(i));
l.push(characterObject);
for (int i = right.length(); i > 0; i--) {
characterObject = new Character(right.charAt(i-1));
r.push(characterObject);
this.left = l;
this.right = r;
public void moveToStart() {
while (! this.left.isEmpty())
this.right.push(this.left.pop());
public String toString() {
tempEs = this;
tempEs.moveToStart();
text = new char[(tempEs.right).size()];
for (int i=0; i < text.length; i++)
text[i] = ((Character) (tempEs.right).pop()).charValue();
return new String(text);
public static void main(String args[]) {
System.out.println("Starting Word processor!");
System.out.println("----------");
EditableString es2 = new EditableString("Hello, how", " are you");
System.out.println("es2: " + es2.toString());
System.out.println("es2: " + es2.toString());
/* Output:
Starting Word processor!
es2: Hello, how are you
es2:
*/

Answer 1

Ok, I tried to create a copy(Es) method and modified the toString() method as follows, but I am having the same problem. Ok, in order to test my methods, I print the various sizes of several stacks. In the toString() method, right after tempEs is declared, this.left=10, this.right=8 and tempEs.left=tempEs.right=0. After the copy method is invoked and assigned to tempEs, this.left=tempEs.left=10 and this.right=tempEs.right=8. Follow me?, this is where I have trouble.
I try to "pop" one value from tempEs.right to see if the action occurs on tempEs and not this. Well, it does. Right after the pop() method, this.left=tempEs.left=10 and this.right=tempEs.right=7. I need this.right to stay at 8. Why are these Editable Strings dependent?
And for the record, I'm not trying to "pay" anyone to do my homework. I am simply trying to pass, and in turn, graduate. This is the second time I am taking this course (failed it with style the 1st time) and desperately need to pass. I have VERY little Java background and this class is unfortunately required for my engineering degree. So, I am simply looking for some help with my 30+hour homework assignments.
public EditableString copy(EditableString ES) {
        EditableString xTemp = new EditableString();
        xTemp.left = ES.left;
        xTemp.right = ES.right;
        return xTemp;
    public String toString() {
        EditableString tempEs = new EditableString();
        tempEs = copy(this);
        tempEs.right.pop();
        tempEs.moveToStart();
        text = new char[(tempEs.right).size()];
        for (int i=0; i < text.length; i++)
            text[i] = ((Character) (tempEs.right).pop()).charValue();
        return new String(text);