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Groovy: A powerful, dynamic language for the JVM
/*
* Copyright 2003-2012 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package groovy.lang;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
/**
* A wrapper for {@link List} which automatically grows the list when either {@link #get(int)} or
* {@link #getAt(int)} is called with an index greater than or equal to {@code size()}.
*
* @author Andre Steingress
* @since 1.8.7
*/
public final class ListWithDefault implements List {
private final List delegate;
private final boolean lazyDefaultValues;
private final Closure initClosure;
private ListWithDefault(List items, boolean lazyDefaultValues, Closure initClosure) {
this.delegate = items;
this.lazyDefaultValues = lazyDefaultValues;
this.initClosure = initClosure;
}
public static List newInstance(List items, boolean lazyDefaultValues, Closure initClosure) {
if (items == null)
throw new IllegalArgumentException("Parameter \"items\" must not be null");
if (initClosure == null)
throw new IllegalArgumentException("Parameter \"initClosure\" must not be null");
return new ListWithDefault(items, lazyDefaultValues, initClosure);
}
public int size() {
return delegate.size();
}
public boolean isEmpty() {
return delegate.isEmpty();
}
public boolean contains(Object o) {
return delegate.contains(o);
}
public Iterator iterator() {
return delegate.iterator();
}
public Object[] toArray() {
return delegate.toArray();
}
public T[] toArray(T[] ts) {
return delegate.toArray(ts);
}
public boolean add(T t) {
return delegate.add(t);
}
public boolean remove(Object o) {
return delegate.remove(o);
}
public boolean containsAll(Collection objects) {
return delegate.containsAll(objects);
}
public boolean addAll(Collection ts) {
return delegate.addAll(ts);
}
public boolean addAll(int i, Collection ts) {
return delegate.addAll(i, ts);
}
public boolean removeAll(Collection objects) {
return delegate.removeAll(objects);
}
public boolean retainAll(Collection objects) {
return delegate.retainAll(objects);
}
public void clear() {
delegate.clear();
}
/**
* Overwrites subscript operator handling by redirecting to {@link #get(int)}.
*
* @param index an index (might be greater or equal to {@code size()}, or smaller than 0)
* @return the value at the given {@code index} or the default value
*/
public T getAt(int index) {
return get(index);
}
/**
* Returns the element at the given index but grows the list if needed. If the requested {@code index} is
* greater than or equal to {@code size()}, the list will grow to the new size and a default value calculated
* using the initClosure will be used to populate the missing value and returned.
*
* If lazyDefaultValues is true any gaps when growing the list are filled
* with nulls. Subsequent attempts to retrieve items from the list from those gap index values
* will, upon finding null, call the initClosure to populate the list for the
* given list value. Hence, when in this mode, nulls cannot be stored in this list.
* If lazyDefaultValues is false any gaps when growing the list are filled
* eagerly by calling the initClosure for all gap indexes during list growth.
* No calls to initClosure are made except during list growth and it is ok to
* store null values in the list when in this mode.
*
* This implementation breaks
* the contract of {@link java.util.List#get(int)} as it a) possibly modifies the underlying list and b) does
* NOT throw an {@link IndexOutOfBoundsException} when {@code index < 0 || index >= size()}.
*
* @param index an index (might be greater or equal to {@code size()}, or smaller than 0)
* @return the value at the given {@code index} or the default value
*/
public T get(int index) {
final int size = size();
int normalisedIndex = normaliseIndex(index, size);
// either index >= size or the normalised index is negative
if (normalisedIndex >= size || normalisedIndex < 0) {
final boolean prepend = (normalisedIndex < 0);
// find out the number of gaps to fill with null/the default value
final int gapCount = (prepend ? ((normalisedIndex + 1) * -1) : normalisedIndex - size);
// fill all gaps
for (int i = 0; i < gapCount; i++) {
final int idx = prepend ? 0 : size();
// if we lazily create default values, use 'null' as placeholder
if (lazyDefaultValues)
delegate.add(idx, null);
else
delegate.add(idx, getDefaultValue(idx));
}
// add the first/last element being always the default value
final int idx = prepend ? 0 : normalisedIndex;
delegate.add(idx, getDefaultValue(idx));
// normalise index again to get positive index
normalisedIndex = normaliseIndex(index, size());
}
T item = delegate.get(normalisedIndex);
if (item == null && lazyDefaultValues) {
item = getDefaultValue(normalisedIndex);
delegate.set(normalisedIndex, item);
}
return item;
}
@SuppressWarnings("unchecked")
private T getDefaultValue(int idx) {
return (T) initClosure.call(new Object[]{idx});
}
private int normaliseIndex(int index, int size) {
if (index < 0) {
index += size;
}
return index;
}
public T set(int i, T t) {
return delegate.set(i, t);
}
public void add(int i, T t) {
delegate.add(i, t);
}
public T remove(int i) {
return delegate.remove(i);
}
public int indexOf(Object o) {
return delegate.indexOf(o);
}
public int lastIndexOf(Object o) {
return delegate.lastIndexOf(o);
}
public ListIterator listIterator() {
return delegate.listIterator();
}
public ListIterator listIterator(int i) {
return delegate.listIterator(i);
}
@Override
public boolean equals(Object obj) {
return delegate.equals(obj);
}
@Override
public int hashCode() {
return delegate.hashCode();
}
/**
* Returns a view of a portion of this list. This method returns a list with the same
* lazy list settings as the original list.
*
* @param fromIndex low endpoint of the subList (inclusive)
* @param toIndex upper endpoint of the subList (exclusive)
* @return a view of a specified range within this list, keeping all lazy list settings
*/
public List subList(int fromIndex, int toIndex) {
return new ListWithDefault(delegate.subList(fromIndex, toIndex), lazyDefaultValues, (Closure) initClosure.clone());
}
}