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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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* accompanied this code).
*
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package java8.util;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java8.util.function.Consumer;
import java8.util.function.DoubleConsumer;
import java8.util.function.IntConsumer;
import java8.util.function.LongConsumer;
/**
* A place for static default implementations of the new Java 8
* default interface methods and static interface methods in the
* {@link Iterator} interface.
*/
public final class Iterators {
/**
* Performs the given action for each remaining element until all elements
* have been processed or the action throws an exception. Actions are
* performed in the order of iteration.
* Exceptions thrown by the action are relayed to the caller.
*
*
* The behavior of an iterator is unspecified if the action modifies the underlying
* source of elements in any way (even by calling the {@link Iterator#remove() remove}
* method or other mutator methods of {@code Iterator} subtypes), unless an overriding
* class has specified a concurrent modification policy.
*
* Subsequent behavior of an iterator is unspecified if the action throws an
* exception.
*
*
The implementation behaves as if:
*
{@code
* while (it.hasNext())
* action.accept(it.next());
* }
*
* @param the type of the elements for the passed iterator
* @param it the {@code Iterator} whose remaining elements should be processed
* @param action The action to be performed for each element
* @throws NullPointerException if the specified iterator is null
* @throws NullPointerException if the specified action is null
* @since 1.8
*/
public static void forEachRemaining(Iterator it, Consumer action) {
Objects.requireNonNull(it);
Objects.requireNonNull(action);
while (it.hasNext()) {
action.accept(it.next());
}
}
/**
* Performs the given action for each remaining element until all elements
* have been processed or the action throws an exception. Actions are
* performed in the order of iteration.
* Exceptions thrown by the action are relayed to the caller.
*
*
* The behavior of an iterator is unspecified if the action modifies the underlying
* source of elements in any way (even by calling the {@link Iterator#remove() remove}
* methodor other mutator methods of {@code Iterator} subtypes), unless an overriding
* class has specified a concurrent modification policy.
*
* Subsequent behavior of an iterator is unspecified if the action throws an
* exception.
*
*
The implementation behaves as if:
*
{@code
* while (it.hasNext())
* action.accept(it.next());
* }
*
* @param it the {@code Iterator} whose remaining elements should be processed
* @param action The action to be performed for each element
* @throws NullPointerException if the specified iterator is null
* @throws NullPointerException if the specified action is null
* @since 1.8
*/
public static void forEachRemaining(PrimitiveIterator.OfInt it, IntConsumer action) {
Objects.requireNonNull(it);
Objects.requireNonNull(action);
while (it.hasNext()) {
action.accept(it.nextInt());
}
}
/**
* Performs the given action for each remaining element until all elements
* have been processed or the action throws an exception. Actions are
* performed in the order of iteration.
* Exceptions thrown by the action are relayed to the caller.
*
*
* The behavior of an iterator is unspecified if the action modifies the underlying
* source of elements in any way (even by calling the {@link Iterator#remove() remove}
* method or other mutator methods of {@code Iterator} subtypes), unless an overriding
* class has specified a concurrent modification policy.
*
* Subsequent behavior of an iterator is unspecified if the action throws an
* exception.
*
*
The implementation behaves as if:
*
{@code
* while (it.hasNext())
* action.accept(it.next());
* }
*
* @param it the {@code Iterator} whose remaining elements should be processed
* @param action The action to be performed for each element
* @throws NullPointerException if the specified iterator is null
* @throws NullPointerException if the specified action is null
* @since 1.8
*/
public static void forEachRemaining(PrimitiveIterator.OfLong it, LongConsumer action) {
Objects.requireNonNull(it);
Objects.requireNonNull(action);
while (it.hasNext()) {
action.accept(it.nextLong());
}
}
/**
* Performs the given action for each remaining element until all elements
* have been processed or the action throws an exception. Actions are
* performed in the order of iteration.
* Exceptions thrown by the action are relayed to the caller.
*
*
* The behavior of an iterator is unspecified if the action modifies the underlying
* source of elements in any way (even by calling the {@link Iterator#remove() remove}
* method or other mutator methods of {@code Iterator} subtypes), unless an overriding
* class has specified a concurrent modification policy.
*
* Subsequent behavior of an iterator is unspecified if the action throws an
* exception.
*
*
The implementation behaves as if:
*
{@code
* while (it.hasNext())
* action.accept(it.next());
* }
*
* @param it the {@code Iterator} whose remaining elements should be processed
* @param action The action to be performed for each element
* @throws NullPointerException if the specified iterator is null
* @throws NullPointerException if the specified action is null
* @since 1.8
*/
public static void forEachRemaining(PrimitiveIterator.OfDouble it, DoubleConsumer action) {
Objects.requireNonNull(it);
Objects.requireNonNull(action);
while (it.hasNext()) {
action.accept(it.nextDouble());
}
}
/**
* Returns an {@link Iterator} that traverses the remaining elements
* covered by the passed enumeration. Traversal is undefined if any
* methods are called on the passed enumeration after the call to
* {@code asIterator}.
*
* API Note:
* This method is intended to help adapt code that produces
* {@code Enumeration} instances to code that consumes {@code Iterator}
* instances. For example, the {@link java.util.jar.JarFile#entries
* JarFile.entries()} method returns an {@code Enumeration}.
* This can be turned into an {@code Iterator}, and then the
* {@code forEachRemaining()} method can be used:
*
* {@code
* JarFile jarFile = ... ;
* Iterators.forEachRemaining(Iterators.asIterator(jarFile.entries()), entry -> ... );
* }
*
* Implementation Requirements:
* The default implementation returns an {@code Iterator} whose
* {@link Iterator#hasNext hasNext} method calls the passed Enumeration's
* {@code hasMoreElements} method, whose {@link Iterator#next next}
* method calls the passed Enumeration's {@code nextElement} method,
* and whose {@link Iterator#remove remove} method throws
* {@code UnsupportedOperationException}.
*
* @param the type of the elements for the passed enumeration
* @param en the {@code Enumeration} whose remaining elements should be processed
* @return an Iterator representing the remaining elements of the
* passed Enumeration
* @throws NullPointerException if the specified enumeration is null
*
* @since 9
*/
public static Iterator asIterator(Enumeration en) {
Objects.requireNonNull(en);
return new ImmutableIt() {
@Override
public boolean hasNext() {
return en.hasMoreElements();
}
@Override
public E next() {
return en.nextElement();
}
};
}
/**
* Returns an iterator that has no elements. More precisely,
*
*
* - {@link Iterator#hasNext hasNext} always returns {@code false}.
* - {@link Iterator#next next} always throws
* {@link NoSuchElementException}.
* - {@link Iterator#remove remove} always throws
* {@link IllegalStateException}.
*
*
*
* Implementations of this method are permitted, but not required, to return
* the same object from multiple invocations.
*
* @param
* type of elements, if there were any, in the iterator
* @return an empty iterator
* @since 1.7
*/
@SuppressWarnings("unchecked")
public static Iterator emptyIterator() {
return (Iterator) EmptyIt.EMPTY_ITERATOR;
}
static Iterator singletonIterator(E e) {
return new ImmutableIt() {
private boolean hasNext = true;
public boolean hasNext() {
return hasNext;
}
public E next() {
if (hasNext) {
hasNext = false;
return e;
}
throw new NoSuchElementException();
}
};
}
static final class EmptyIt extends ImmutableIt {
static final EmptyIt