iteration newby question

[davikokar]

Hallo,

I have an arraylist containing objects. I would like to iterate it and confront one of the properties ("name") of the object with a string. If they match I return the object.
I don't know how to compare the present object property of the iteration with the string, and how to return the matching one.

The code I have till now:

public myObject find(String criteria)
{
  int i=1;
  Iterator<myObject> it = this.myArrayList.iterator();
  while (it.hasNext())
  {
    if (((it.next())).equals(criteria)¨
      {return ...?...}
    else
      i++;
  }

 

[jaxtell]

Assuming the class myObject (should probably be MyObject to follow naming conventions) has a public getName() method that returns a String, and you want to return null if there is no match,

public myObject find(String criteria)
{
  int i=1;
  myObject temp = null;
  Iterator<myObject> it = this.myArrayList.iterator();
  while (it.hasNext())
  {
    temp = it.next();
    if (temp.getName()).equals(criteria)¨
      {break;}

  }
  return temp;

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[tom62]

Or you could do the following:

public myObject find(String criteria) {
   for (myObject obj : myArrayList) {
      if (obj.getName().equals(criteria))¨
         return obj;
   }
   return null;
}

 

[Diancecht]

It depends on how the name property is coded.

If you want to keep the property private you can code a isSameName method that will compare the values.

Cheers,
Dian

 

[stefanwagner]

A List of matching results can be more appropriate...

public List <MyObject> find (String criteria)
{
	List <MyObject> results = new ArrayList <myObject> ();

	for (MyObject mo : myArrayList)
	{
		if (mo.getName ()).matches (criteria))
		{
			results.add (mo);
		}
	}
	return results;
}

	// usage:
	List <MyObject> l1 = find (".*foo.*");
	for (MyObject myObject : l1)
	{
		myObject.doSomething ();
	}

...and is more easy to use, than a method which might return null (NullPointerException) - an empty list is a natural thing.

Yes - you want to change myObject to MyObject.

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