printList problem
Hi
I'm having problems getting java to print out the list below using printList. I just get the numbers of the list printed out like this:
0
1
2
3
4
5
=============
process completed
Any ideas on what i've done wrong?
Thanks
import java.util.*;
class pracB3
{
publicstaticvoid printList(List L)
{
String nextName;
for (int i=0; i<L.size(); i++)
{
nextName = (String) L.get(i);
System.out.println(i);
}
System.out.println("=============");
}
publicstaticvoid main(String[] args)
{
List names =new LinkedList();
names.add("Jones, M");
names.add("Smith, J");
names.add("Bloggs, F");
names.add("Thompson, A ");
names.add("McCullough, G");
names.add("Ling, Y ");
printList(names);
}
}
>
[1673 byte] By [
jclegsa] at [2007-11-26 18:54:43]
for (int i=0; i<L.size(); i++)
{
nextName = (String) L.get(i);
System.out.println(nextName );// ><-- nextName !!!
}
Thanks for your help! I'm an idiot, knew it was something stupid like that!
I'm also having trouble with the searching of the List. I have written the following method mySearchList and tried to return it but it says:
I:\Java practicals\pracB3\pracB3a.java:31: variable position might not have been initialized
return position;
I have been trying to just return the position of the String and not the String itself.
Thanks
import java.util.*;
class pracB3a
{
public static void printList(List L)
{
String nextName;
for (int i=0; i<L.size(); i++)
{
nextName = (String) L.get(i);
System.out.println(nextName);
}
System.out.println("=============");
}
public static int mySearchList (List L, String item)
{
int position;
String nextN;
for (int i=0; i><L.size(); i++)
{
nextN = (String) L.get(i);
position = mySearchList(L, item);
}
return position;
}
public static void main(String[] args)
{
List names = new LinkedList();
names.add("Jones, M");
names.add("Smith, J");
names.add("Bloggs, F");
names.add("Thompson, A ");
names.add("McCullough, G");
names.add("Ling, Y ");
names.add(2, "Young, M");
printList(names);
}
}
>
There is no need for recursion in your search method. Just loop thru the items in the list, and return i when you find a match. Also, it is possible that the item passed in to the method does not exist in the list, and in that case position will no be have a value assigned, and java does not initialize local variables to a default, so you need to do that yourself. A safe default value would be -1, since list indexes start at 0.
public static int mySearchList (List L, String item)
{
int position = -1;
String nextN;
for (int i=0; i<L.size(); i++)
{
nextN = (String) L.get(i);
if(nextN.trim().equalsIgnoreCase(item.trim()))
return i;
}
return position;
}
Also, note that to compare strings, you need to use .equals() not ==, and that it is also a good idea to trim off whitespace when comparing (unless it is significant) and to ignore case.
~Tim
Message was edited by:
SomeoneElse>
You don't need recursion.
public static int mySearchList (List L, String item)
{
int position = -1;// nothing found
for (int i=0; i<L.size(); i++)
{
position = L.indexOf(item);
if (position >= 0) {
break; // found something (first occurance of item)
}
}
return position;
}
EDIT: Tim was quicker. The difference is that Tims method returns the last match, mine the first. No other differences really
Message was edited by:
PhHein
Thanks for all your help!!Much appreciated
