Solved

ArrayList Iterator Problem

Posted on 2008-10-19
2
899 Views
Last Modified: 2008-11-17
I am trying to loop though an ArrayList and remove all even numbers.  But I am having trouble with Integer to Object conversions.  Or am I going about the whole thing wrong?   There will always be only integers in this ArrayList and I need to do this with Iterators.

Thanks



import java.util.*; 
import java.lang.*;
import java.io.*; 
 
class IteratorDemo { 
public static void main(String args[]) { 
 
ArrayList<Integer> myLIST = new ArrayList<Integer>();   //Create List
 
 //Add Items to LIst
myLIST.add(3); 
myLIST.add(8); 
myLIST.add(4); 
myLIST.add(1); 
myLIST.add(9); 
myLIST.add(7); 
myLIST.add(2); 
myLIST.add(5); 
myLIST.add(6); 
 
 
 
// use iterator to display contents of myLIST 
System.out.print("Standard Output: "); 
 
Iterator itrX = myLIST.iterator();   //define Iterator and attach to mylist
 
while(itrX.hasNext()) {         //loop through items while there are items to loop through.
 
Object element = itrX.next(); 
System.out.print(element + " ");   // print out element
 
} 
 
System.out.println();   //BlankLine
 
 
// Go back through the list and delete all even numbers
System.out.print("Only Odds: "); 
itrX = myLIST.iterator();
while(itrX.hasNext()) {
 
Object intEL = itrX.next();
 
 
 
if( intEL %2==0 ){
 itrX.remove();         
}
} 
 
}
}

Open in new window

0
Comment
Question by:PriceConsulting
2 Comments
 
LVL 59

Accepted Solution

by:
Kevin Cross earned 500 total points
ID: 22752901
Either use the generic Iterator<E> like this:
Iterator<Integer> itrX = myLIST.iterator();
Integer element = itrX.next();  // retrieving iterator.next() as Integer

OR you will have to cast the result of .next() to an Integer like this:
Iterator itrX = myLIST.iterator();
Integer element = (Integer)itrX.next();

Since you are already dealing with the generic version fo ArrayList, I would highly suggest option 1.
0
 
LVL 2

Expert Comment

by:szigeti
ID: 22952969
Here ya go:

I added a loop to print out the filtered odd numbers at the end, and changed:

Iterator itrX = myLIST.iterator();
to:
Iterator<Integer> itrX = myLIST.iterator();

and

Object intEL = itrX.next();
to
Integer intEL = itrX.next();

import java.util.*; 
import java.lang.*;
import java.io.*; 
 
class IteratorDemo { 
public static void main(String args[]) { 
 
ArrayList<Integer> myLIST = new ArrayList<Integer>();   //Create List
 
 //Add Items to LIst
myLIST.add(3); 
myLIST.add(8); 
myLIST.add(4); 
myLIST.add(1); 
myLIST.add(9); 
myLIST.add(7); 
myLIST.add(2); 
myLIST.add(5); 
myLIST.add(6); 
 
 
 
// use iterator to display contents of myLIST 
System.out.print("Standard Output: "); 
 
Iterator<Integer> itrX = myLIST.iterator();   //define Iterator and attach to mylist
 
while(itrX.hasNext()) {         //loop through items while there are items to loop through.
 
Integer element = itrX.next(); 
System.out.print(element + " ");   // print out element
 
} 
 
System.out.println();   //BlankLine
 
 
// Go back through the list and delete all even numbers
 
itrX = myLIST.iterator();
while(itrX.hasNext()) {
 
Integer intEL = itrX.next();
 
 
 
if( intEL %2==0 ){
 itrX.remove();         
}
} 
 
// Added another loop to print out the remaining odd numbers:
itrX = myLIST.iterator();
System.out.print("Only Odds: "); 
while(itrX.hasNext()) {         //loop through items while there are items to loop through.
	 
	Integer element = itrX.next(); 
	System.out.print(element + " ");   // print out element
	 
	} 
 
}
}

Open in new window

0

Featured Post

Free Tool: Port Scanner

Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
custom annotations 9 42
login jsp example 24 63
printf performancy 11 67
Finding all private fields and their corresponding getters setters for nested classes 4 13
For beginner Java programmers or at least those new to the Eclipse IDE, the following tutorial will show some (four) ways in which you can import your Java projects to your Eclipse workbench. Introduction While learning Java can be done with…
Java Flight Recorder and Java Mission Control together create a complete tool chain to continuously collect low level and detailed runtime information enabling after-the-fact incident analysis. Java Flight Recorder is a profiling and event collectio…
This tutorial covers a practical example of lazy loading technique and early loading technique in a Singleton Design Pattern.
This theoretical tutorial explains exceptions, reasons for exceptions, different categories of exception and exception hierarchy.

808 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question