Question

Possible Duplicate:
Search for a regexp in a java arraylist

Is there a way to access items stored in a List using regular expressions?

Take the following code as an example:

String jpg  = "page1.jpg";
String jpeg = "page-2.jpeg";
String png  = "page-003.png";

ArrayList<String> images = new ArrayList<String>();
images.add( jpg );
images.add( jpeg );
images.add( png );

Pattern regex = Pattern.compile( "\\D{4,5}0*1.\\w{3,4}" );
int index = images.indexOf( regex );

if( index != -1 )
    System.out.println( "Did find the string" );
else
    System.out.println( "Didn't find the string" );

The code above does not work in finding the string page1.jpg and instead returns -1.

Is there a way that this can be achieved without iterating through the List and checking whether a string matches a regex?

Answer 1

Not really. Short of subclassing ArrayList or using scala, groovy, etc, there isn’t. indexOf uses the equals method, so you’re stuck.

If you’re willing to use dark arts, you could create a custom class with a equals method that uses the regex.

int index = images.indexOf(new Object() {
    public boolean equals(Object obj) {
        return regex.matches(obj.toString());
    }
});

But I’d just iterate. It’s cleaner. You’re co-workers and yourself in 6-months time will appreciate it.