Created
July 31, 2014 19:27
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Example on implementing an iterator
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package com.EmpowerOperations.LinqALike.Queries; | |
import com.EmpowerOperations.LinqALike.Delegate.Func1; | |
import java.util.Iterator; | |
public class SelectQuery<TElement, TResult> implements DefaultQueryable<TResult> { | |
private final Iterable<TElement> set; | |
private final Func1<? super TElement, TResult> targetSite; | |
public SelectQuery(Iterable<TElement> set, Func1<? super TElement, TResult> targetSite) { | |
assert set != null; | |
assert targetSite != null; | |
this.set = set; | |
this.targetSite = targetSite; | |
} | |
@Override | |
public Iterator<TResult> iterator() { | |
return new SelectIterator<>(set.iterator(), targetSite); | |
} | |
private class SelectIterator<TElement, TResult> implements Iterator<TResult>{ | |
private final Iterator<TElement> baseIterator; | |
private final Func1<? super TElement, TResult> transform; | |
public SelectIterator(Iterator<TElement> baseIterator, Func1<? super TElement, TResult> transform){ | |
this.baseIterator = baseIterator; | |
this.transform = transform; | |
} | |
@Override | |
public boolean hasNext() { | |
return baseIterator.hasNext(); | |
} | |
@Override | |
public TResult next() { | |
return transform.getFrom(baseIterator.next()); | |
} | |
@Override | |
public void remove() { | |
throw new UnsupportedOperationException(); | |
} | |
} | |
} |
Notice that my outer class, implements DefaultQueryable<TElement>
, which is a version of Iterable<TElement>
(not, iter- ator ), and it has a method called iterator() that returns a SelectIterator<TElement>
. It is a little confusing with so many generics flying around.
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Hey @Bghyun, take a look at this, maybe itl make some sense