Can someone spot an error here?

[Xara Mithra]

I took this partial prrogram from JavaRules Vol 2 :
------------------------------------------------
public class StringBuffer{
public StringBuffer() {
this(16);
}
public StringBuffer(int length) {
value = new char[length];
shared = false;
}
public StringBuffer(String str) {
this(str.length() + 16);
append(str);
}
public static void main(String args[])
{
}
}
Errors :
---------
StringBuffer.java:8: cannot resolve symbol
symbol : variable value
location: class StringBuffer
value = new char[length];
^
StringBuffer.java:9: cannot resolve symbol
symbol : variable shared
location: class StringBuffer
shared = false;
^
StringBuffer.java:14: cannot resolve symbol
symbol : method append (java.lang.String)
location: class StringBuffer
append(str);
^
3 errors
Suggest : Can someone suggest what to write in main() method. So I understand these constructors?
Sorry if the questions are too silly

[Simon Klaiber]

You have to declare the variables...
If you want them local (what i don't think) use:

char[] value = new char[length];

and

boolean shared = false;

If you want them as instance variables (what I do think you want)
declare them inside the class but outside the methods as

private char[] value;

and

private boolean shared;

if you want to use

append(str);

You need a method called append that takes a String object as parameter:
for example:

public void append(String inStr) {
    //do great appending stuff
}

or

private void append(String inStr) {
    //do great appending stuff
}

if you want to encapsulate the method within the constructors or other public methods.
BTW when you use

this.append(str);

it does the same as

append(str);

but makes the code easier to read.
Simon
[ November 20, 2003: Message edited by: Simon Klaiber ]
[ November 20, 2003: Message edited by: Simon Klaiber ]