S Keith

Its all to do with the variables scope.

In java we can have the following types of variables:

instance variables
class variables
local variables

They have different scopes. Instance variables are 'alive' if the object they live in is alive.

Class variables are alive when the class is loaded.

Local variables are alive if the method they live in is still on the stack.

Parameters are local variables.

The variables you were referring to are local variables with the same names but in different methods, and different classes.




Theres more to this. Anyone have a link?
[ March 24, 2008: Message edited by: S Keith ]

Heres some code that should explain things.

I've tried to keep it similar to the code you gave.

import java.util.*; import java.io.*; class Test{ public static void main(String [] args){ ArrayList<File> foo = new ArrayList<File>(); foo.add(new File("bob")); new Test().createCheckBoxes(foo); } private void createCheckBoxes(List<File> javaFiles) { int count = javaFiles.size(); Iterator<File> it = javaFiles.iterator() ; while ( it.hasNext()){ String s = (it.next()).getName() ; // use some string functions System.out.println(s + " in upper case is " + s.toUpperCase()); System.out.println(s + " is " + s.length() + " characters long"); } } }

running this gives:
C:\Users\Steven\Desktop>javac Test.java C:\Users\Steven\Desktop>java Test bob in upper case is BOB bob is 3 characters long C:\Users\Steven\Desktop>



http://java.sun.com/javase/6/docs/api/java/lang/String.html

howdy.

Can you give me your input file?

If you test it with

foo bar baz

there is no problem.


This is exactly what i have in the file run0.java
import java.io.*; class ListT { public class Node { public String data = ""; public Node link; public Node() { } public Node(String data) { this.data = data; } } public static Node first,last,current,previous,newLink; public static String key; public ListT() { first = null; } public void insert(BufferedReader infile) throws IOException { while ((key = infile.readLine()) != null) { previous = null; current = first; Node newLink = new Node(key); while((current != null) && (key.compareTo(current.data) > 0)) { previous = current; current = current.link; } if (previous == null) { first = newLink; } else { previous.link = newLink; //printList(); } newLink.link = current; } //return first; } public static void printList() { newLink = first; while(newLink != null) { System.out.println(newLink.data + " " + newLink.link); newLink = newLink.link; } } } public class run0 { private static BufferedReader infile; private static PrintWriter outfile; private static String s0; public static ListT l = new ListT(); public static void main(String[] args) throws IOException { infile = new BufferedReader(new FileReader(args[0])); //outfile = new PrintWriter(args[1]); l.insert(infile); l.printList(); infile.close(); //outfile.close(); this is for later } }

and i get the output:

C:\Users\Steven\Desktop>java run0 testfile.txt bar ListT$Node@addbf1 baz ListT$Node@42e816 foo null C:\Users\Steven\Desktop>
[ March 24, 2008: Message edited by: S Keith ]

I tried it with the file: foo, bar, baz

You have a printList(); call in insert making it appear that you have duplicates.

The call to printList will also stop you properly linking the list because the newLink reference is tampered with, before the link field innewLink is set.

if you move newLink.link = current; above the call, then that would fix the problem, and you will see that the whole list is printed twice.

newLink.link = current; if (previous == null) { first = newLink; } else { previous.link = newLink; printList(); }

if you take out:

else { previous.link = newLink; printList(); <-- this }

then you will get your list printed ok

[ March 23, 2008: Message edited by: S Keith ]
[ March 23, 2008: Message edited by: S Keith ]