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A general and simple library for Android
/*
* Copyright (C) 2016, 2017, 2018, 2019 HaiYang Li
*
* 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 com.landawn.abacus.util.stream;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import com.landawn.abacus.annotation.Internal;
import com.landawn.abacus.util.N;
import com.landawn.abacus.util.ObjIterator;
import com.landawn.abacus.util.function.Supplier;
/**
*
*/
@Internal
public abstract class ObjIteratorEx extends ObjIterator implements IteratorEx {
@SuppressWarnings("rawtypes")
public static final ObjIteratorEx EMPTY = new QueuedIterator(0) {
@Override
public boolean hasNext() {
return false;
}
@Override
public Object next() {
throw new NoSuchElementException();
}
@Override
public void skip(long n) {
// Do nothing.
}
@Override
public long count() {
return 0;
}
@Override
public void close() {
// Do nothing.
}
};
public static ObjIteratorEx empty() {
return EMPTY;
}
@SafeVarargs
public static ObjIteratorEx of(final T... a) {
return a == null ? EMPTY : of(a, 0, a.length);
}
public static ObjIteratorEx of(final T[] a, final int fromIndex, final int toIndex) {
N.checkFromToIndex(fromIndex, toIndex, N.len(a));
if (fromIndex == toIndex) {
return EMPTY;
}
return new QueuedIterator(toIndex - fromIndex) {
private int cursor = fromIndex;
@Override
public boolean hasNext() {
return cursor < toIndex;
}
@Override
public T next() {
if (cursor >= toIndex) {
throw new NoSuchElementException();
}
return a[cursor++];
}
@Override
public void skip(long n) {
N.checkArgNotNegative(n, "n");
cursor = n < toIndex - cursor ? cursor + (int) n : toIndex;
}
@Override
public long count() {
return toIndex - cursor;
}
@Override
public A[] toArray(A[] output) {
if (output.length < toIndex - cursor) {
output = N.copyOf(output, toIndex - cursor);
}
N.copy(a, cursor, output, 0, toIndex - cursor);
return output;
}
@Override
public List toList() {
return N.asList((T[]) toArray());
}
@Override
public void close() {
// Do nothing.
}
};
}
public static ObjIteratorEx of(final Collection c) {
if (c == null) {
return empty();
}
final Iterator iter = c.iterator();
return new QueuedIterator(c.size()) {
@Override
public boolean hasNext() {
return iter.hasNext();
}
@Override
public T next() {
return iter.next();
}
@Override
public void close() {
// Do nothing.
}
};
}
public static ObjIteratorEx of(final Iterator iter) {
if (iter == null) {
return empty();
} else if (iter instanceof ObjIteratorEx) {
return ((ObjIteratorEx) iter);
}
return new ObjIteratorEx() {
@Override
public boolean hasNext() {
return iter.hasNext();
}
@Override
public T next() {
return iter.next();
}
@Override
public void close() {
// Do nothing.
}
};
}
public static ObjIteratorEx of(final Iterable iterable) {
return iterable == null ? ObjIteratorEx. empty() : of(iterable.iterator());
}
/**
* Lazy evaluation.
*
* @param iteratorSupplier
* @return
*/
public static ObjIteratorEx of(final Supplier> iteratorSupplier) {
N.checkArgNotNull(iteratorSupplier, "iteratorSupplier");
return new ObjIteratorEx() {
private Iterator iter = null;
private ObjIteratorEx iterEx = null;
private boolean isInitialized = false;
@Override
public boolean hasNext() {
if (isInitialized == false) {
init();
}
return iter.hasNext();
}
@Override
public T next() {
if (isInitialized == false) {
init();
}
return iter.next();
}
@Override
public void skip(long n) {
N.checkArgNotNegative(n, "n");
if (isInitialized == false) {
init();
}
if (iterEx != null) {
iterEx.skip(n);
} else {
super.skip(n);
}
}
@Override
public long count() {
if (isInitialized == false) {
init();
}
if (iterEx != null) {
return iterEx.count();
} else {
return super.count();
}
}
@Override
public void close() {
if (isInitialized == false) {
init();
}
if (iterEx != null) {
iterEx.close();
}
}
private void init() {
if (isInitialized == false) {
isInitialized = true;
iter = iteratorSupplier.get();
iterEx = iter instanceof ObjIteratorEx ? (ObjIteratorEx) iter : null;
}
}
};
}
/**
* Lazy evaluation.
*
* @param arraySupplier
* @return
*/
public static ObjIteratorEx oF(final Supplier arraySupplier) {
N.checkArgNotNull(arraySupplier, "arraySupplier");
return new ObjIteratorEx() {
private ObjIteratorEx iterEx = null;
private boolean isInitialized = false;
@Override
public boolean hasNext() {
if (isInitialized == false) {
init();
}
return iterEx.hasNext();
}
@Override
public T next() {
if (isInitialized == false) {
init();
}
return iterEx.next();
}
@Override
public void skip(long n) {
N.checkArgNotNegative(n, "n");
if (isInitialized == false) {
init();
}
iterEx.skip(n);
}
@Override
public long count() {
if (isInitialized == false) {
init();
}
return iterEx.count();
}
private void init() {
if (isInitialized == false) {
isInitialized = true;
iterEx = ObjIteratorEx.of(arraySupplier.get());
}
}
};
}
@Override
public void skip(long n) {
N.checkArgNotNegative(n, "n");
while (n > 0 && hasNext()) {
next();
n--;
}
}
@Override
public long count() {
long result = 0;
while (hasNext()) {
next();
result++;
}
return result;
}
@Override
public void close() {
// Do nothing.
}
static abstract class QueuedIterator extends ObjIteratorEx {
private final int max;
QueuedIterator(int max) {
this.max = max;
}
public int max() {
return max;
}
}
}