Structuring Data with Java - Java - page 277

tedOperationException if they ever get called. My remove( ) method does this. Note that
UnsupportedOperationException is subclassed from RuntimeException , so it is not re-
quired to be declared or caught.

This code is unrealistic in several ways, but it does show the syntax and demonstrates how
the Iterator interface works. In real code, the Iterator and the data are usually separate
objects (the Iterator might be an inner class from the data store class). Also, you don't
even need to write this code for an array; you can just construct an ArrayList object, copy
the array elements into it, and ask it to provide the Iterator . However, I believe it's worth
showing this simple example of the internals of an Iterator so that you can understand both
how it works and how you could provide one for a more sophisticated data structure, should
the need arise.

The Iterable interface has only one nondefault method, iterator() , which must provide
an Iterator for objects of the given type. Because the ArrayIterator class implements
this as well, we can use an object of type ArrayIterator in a “foreach” loop:

structure/ArrayIteratorDemo.java

package package structure ;

import import com.darwinsys.util.ArrayIterator com.darwinsys.util.ArrayIterator ;

public public class class ArrayIteratorDemo ArrayIteratorDemo {

private private final static String [] names = {

"rose" , "petunia" , "tulip"

final static

};

public public static void main ( String [] args ) {

ArrayIterator < String > arrayIterator = new

static void

new ArrayIterator <>( names );

// Java 5, 6 way
for

for ( String s : arrayIterator ) {
System . out . println ( s );

}

// Java 8 way
arrayIterator . forEach ( s -> System . out . println ( s ));

}

}