com.artemis.utils.IntBagIterator Maven / Gradle / Ivy
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package com.artemis.utils;
import java.util.NoSuchElementException;
/**
* Base iterator for {@link IntBag}
*
* example use
*
* IntBag ids;
* ....
* final IntBagIterator it = new IntBagIterator(ids);
* while (it.hasNext())
* doSomething(it.next());
*
* or
*
* for (final IntBagIterator it = new IntBagIterator(ids); it.hasNext();)
* doSomething(it.next());
*
* @author nicolaichuk
*/
public class IntBagIterator {
protected static enum State {
INIT,
NEXT_CALLED,
REMOVE_CALLED,
}
protected final IntBag intBag;
protected int index;
protected int indexEnd;
protected State state;
/**
* Create iterator for IntBag
*
* @return true if the iteration has more elements
*/
public IntBagIterator(final IntBag intBag) {
this.intBag = intBag;
index = -1;
indexEnd = intBag != null ? intBag.size() : 0;
assert indexEnd >= 0;
state = State.INIT;
}
/**
* Create iterator for IntBag
*
* @return true if the iteration has more elements
*/
public IntBagIterator(final IntBag intBag, final int indexBegin) {
this.intBag = intBag;
assert indexBegin >= 0;
this.index = indexBegin - 1;
indexEnd = intBag != null ? intBag.size() : 0;
assert indexEnd >= 0;
state = State.INIT;
}
/**
* Create iterator for IntBag
*
* @return true if the iteration has more elements
*/
public IntBagIterator(final IntBag intBag, final int indexBegin, final int size) {
this.intBag = intBag;
assert indexBegin >= 0;
this.index = indexBegin - 1;
indexEnd = indexBegin + size;
final int allSize = intBag != null ? intBag.size() : 0;
indexEnd = intBag != null ? (indexEnd < allSize ? indexEnd : allSize) : 0;
assert indexEnd >= 0;
state = State.INIT;
}
/**
* return current index
* This method can be called only per call to next().
* This method can not be called after call remove().
*
* @throws IllegalStateException - if the next() method has not yet been called
*/
public int getCurrentIndex() {
if (state == State.NEXT_CALLED && index < indexEnd && indexEnd <= intBag.size()) {
return index;
}
throw new IllegalStateException(getErrorMessage(index));
}
/**
* Returns true if the iteration has more elements. (In other words, returns true if next() would return an element rather than throwing an exception.)
*
* @return true if the iteration has more elements
*/
public boolean hasNext() {
return index + 1 < indexEnd && indexEnd <= intBag.size();
}
/**
* Returns the next element in the iteration.
*
* @return the next element in the iteration
* @throws NoSuchElementException - if the iteration has no more elements
*/
public int next() {
final int newIndex = index + 1;
if (newIndex < indexEnd && indexEnd <= intBag.size()) {
index = newIndex;
state = State.NEXT_CALLED;
return intBag.getData()[index];
}
throw new NoSuchElementException(getErrorMessage(newIndex));
}
/**
* Removes from the underlying collection the last element returned by this iterator (optional operation).
* This method can be called only once per call to next().
* The behavior of an iterator is unspecified if the underlying collection is modified while the iteration is in progress in any way other than by calling this method.
*
* @throws IllegalStateException - if the next() method has not yet been called, or the remove() method has already been called after the last call to the next() method
*/
public void remove() {
if (state == State.NEXT_CALLED && index < indexEnd && indexEnd <= intBag.size()) {
state = State.REMOVE_CALLED;
intBag.removeIndex(index);
index--;
indexEnd--;
assert index < indexEnd;
} else {
throw new IllegalStateException(getErrorMessage(index));
}
}
/**
* generate error message
*/
private String getErrorMessage(final int indexVal) {
final String message = "Tried accessing element: " + indexVal + "/" + indexEnd + "/" + intBag.size() + "/" + state.name();
return message;
}
}