102 lines
2.0 KiB
Java
102 lines
2.0 KiB
Java
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package net.sourceforge.tuned;
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import java.util.Iterator;
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import java.util.NoSuchElementException;
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public class FunctionIterator<S, T> implements Iterator<T> {
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/**
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* A Function transforms one Object into another.
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*
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* @param <S> type of source Objects
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* @param <T> type Objects are transformed into
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*/
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public static interface Function<S, T> {
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/**
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* Transform the given sourceValue into any kind of Object.
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*
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* @param sourceValue - the Object to transform
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* @return the transformed version of the object
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*/
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public T evaluate(S sourceValue);
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}
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private final Iterator<S> sourceIterator;
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private final Function<S, T> function;
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public FunctionIterator(Iterable<S> source, Function<S, T> function) {
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this(source.iterator(), function);
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}
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public FunctionIterator(Iterator<S> iterator, Function<S, T> function) {
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this.sourceIterator = iterator;
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this.function = function;
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}
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@Override
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public boolean hasNext() {
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try {
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return peekNext() != null;
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} catch (Exception e) {
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return true;
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}
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}
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@Override
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public T next() {
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if (!hasNext())
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throw new NoSuchElementException();
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try {
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return peekNext();
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} finally {
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cache = null;
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currentException = null;
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}
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}
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private T cache = null;
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private RuntimeException currentException = null;
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private T peekNext() {
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while (cache == null && (sourceIterator.hasNext() || currentException != null)) {
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if (currentException != null)
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throw currentException;
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try {
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cache = transform(sourceIterator.next());
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} catch (RuntimeException e) {
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currentException = e;
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}
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}
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return cache;
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}
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private T transform(S sourceValue) {
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return function.evaluate(sourceValue);
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}
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/**
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* The remove operation is not supported by this implementation of <code>Iterator</code>.
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*
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* @throws UnsupportedOperationException if this method is invoked.
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* @see java.util.Iterator
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*/
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@Override
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public void remove() {
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throw new UnsupportedOperationException();
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}
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}
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