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Sequence.java
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Sequence.java
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/*
* JBoss, Home of Professional Open Source
* Copyright 2009, JBoss Inc., and individual contributors as indicated
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.xnio;
import java.io.Serializable;
import java.util.Iterator;
import java.util.Arrays;
import java.util.Collection;
import java.util.AbstractList;
import java.util.List;
import java.util.RandomAccess;
/**
* An immutable sequence of elements. Though this class implements {@link java.util.List}, it is in fact
* immutable.
*
* @param <T> the element type
*/
public final class Sequence<T> extends AbstractList<T> implements List<T>, RandomAccess, Serializable {
private static final long serialVersionUID = 3042164316147742903L;
private final Object[] values;
private static final Object[] empty = new Object[0];
private Sequence(final Object[] values) {
final Object[] realValues = values.clone();
this.values = realValues;
for (Object realValue : realValues) {
if (realValue == null) {
throw new NullPointerException("value member is null");
}
}
}
private static final Sequence<?> EMPTY = new Sequence(empty);
/**
* Return a sequence of the given members.
*
* @param members the members
* @param <T> the element type
* @return a sequence
*/
public static <T> Sequence<T> of(T... members) {
if (members.length == 0) {
return empty();
} else {
return new Sequence<T>(members);
}
}
/**
* Return a sequence of the given members.
*
* @param members the members
* @param <T> the element type
* @return a sequence
*/
public static <T> Sequence<T> of(Collection<T> members) {
if (members instanceof Sequence) {
return (Sequence<T>) members;
}
final Object[] objects = members.toArray();
if (objects.length == 0) {
return empty();
}
return new Sequence<T>(objects);
}
/**
* Cast a sequence to a different type <b>if</b> all the contained elements are of the subtype.
*
* @param newType the class to cast to
* @param <N> the new type
* @return the typecast sequence
* @throws ClassCastException if any elements could not be cast
*/
@SuppressWarnings("unchecked")
public <N> Sequence<N> cast(Class<N> newType) throws ClassCastException {
for (Object value : values) {
newType.cast(value);
}
return (Sequence<N>) this;
}
/**
* Return an empty sequence.
*
* @param <T> the element type
* @return the empty sequence
*/
@SuppressWarnings("unchecked")
public static <T> Sequence<T> empty() {
return (Sequence<T>) EMPTY;
}
/**
* Get an iterator over the elements of this sequence.
*
* @return an iterator over the elements of this sequence
*/
@SuppressWarnings("unchecked")
public Iterator<T> iterator() {
return Arrays.<T>asList((T[]) values).iterator();
}
/**
* Return the number of elements in this sequence.
*
* @return the number of elements
*/
public int size() {
return values.length;
}
/**
* Determine whether this sequence is empty.
*
* @return {@code true} if the sequence has no elements
*/
public boolean isEmpty() {
return values.length == 0;
}
/**
* Get a copy of the values array.
*
* @return a copy of the values array
*/
public Object[] toArray() {
return values.clone();
}
/**
* Get the value at a certain index.
*
* @param index the index
* @return the value
*/
@SuppressWarnings("unchecked")
public T get(final int index) {
return (T) values[index];
}
/**
* Determine whether this sequence is equal to another.
*
* @param other the other sequence
* @return {@code true} if they are equal, {@code false} otherwise
*/
public boolean equals(Object other) {
return other instanceof Sequence && equals((Sequence<?>)other);
}
/**
* Determine whether this sequence is equal to another.
*
* @param other the other sequence
* @return {@code true} if they are equal, {@code false} otherwise
*/
public boolean equals(Sequence<?> other) {
return this == other || other != null && Arrays.equals(values, other.values);
}
/**
* Get the hash code for this sequence.
*
* @return the hash code
*/
public int hashCode() {
return Arrays.hashCode(values);
}
}