OnJava8-Examples/collections/AdapterMethodIdiom.java

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// collections/AdapterMethodIdiom.java
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// (c)2020 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://OnJava8.com for more book information.
// The "Adapter Method" idiom uses for-in
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// with additional kinds of Iterables
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import java.util.*;
class ReversibleArrayList<T> extends ArrayList<T> {
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ReversibleArrayList(Collection<T> c) {
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super(c);
}
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public Iterable<T> reversed() {
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return new Iterable<T>() {
public Iterator<T> iterator() {
return new Iterator<T>() {
int current = size() - 1;
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public boolean hasNext() {
return current > -1;
}
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public T next() { return get(current--); }
public void remove() { // Not implemented
throw new UnsupportedOperationException();
}
};
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}
};
}
}
public class AdapterMethodIdiom {
public static void main(String[] args) {
ReversibleArrayList<String> ral =
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new ReversibleArrayList<String>(
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Arrays.asList("To be or not to be".split(" ")));
// Grabs the ordinary iterator via iterator():
for(String s : ral)
System.out.print(s + " ");
System.out.println();
// Hand it the Iterable of your choice
for(String s : ral.reversed())
System.out.print(s + " ");
}
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}
/* Output:
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To be or not to be
be to not or be To
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*/