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A general programming library in Java/Android. It's easy to learn and simple to use with concise and powerful APIs.
/*
* 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 java.util.function.Supplier;
import com.landawn.abacus.annotation.Internal;
import com.landawn.abacus.util.N;
import com.landawn.abacus.util.ObjIterator;
/**
*
*/
@Internal
public abstract class ObjIteratorEx extends ObjIterator implements IteratorEx {
@SuppressWarnings("rawtypes")
public static final ObjIteratorEx EMPTY = new BufferedIterator(0) { //NOSONAR
@Override
public boolean hasNext() {
return false;
}
@Override
public Object next() {
throw new NoSuchElementException();
}
@Override
public void advance(long n) {
// Do nothing.
}
@Override
public long count() {
return 0;
}
@Override
public void close() {
// Do nothing.
}
};
public static ObjIteratorEx empty() { //NOSONAR
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 BufferedIterator(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 advance(long n) {
cursor = n < toIndex - cursor ? cursor + (int) n : toIndex;
}
@Override
public long count() {
return toIndex - cursor; //NOSONAR
}
@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 BufferedIterator(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 arraySupplier
// * @return
// */
// public static ObjIteratorEx from(final Supplier arraySupplier) {
// N.checkArgNotNull(arraySupplier, "arraySupplier");
//
// return new ObjIteratorEx<>() {
// private ObjIteratorEx iterEx = null;
// private boolean isInitialized = false;
//
// @Override
// public boolean hasNext() {
// if (!isInitialized) {
// init();
// }
//
// return iterEx.hasNext();
// }
//
// @Override
// public T next() {
// if (!isInitialized) {
// init();
// }
//
// return iterEx.next();
// }
//
// @Override
// public void advance(long n) {
// if (!isInitialized) {
// init();
// }
//
// iterEx.advance(n);
// }
//
// @Override
// public long count() {
// if (!isInitialized) {
// init();
// }
//
// return iterEx.count();
// }
//
// private void init() {
// if (!isInitialized) {
// isInitialized = true;
// iterEx = ObjIteratorEx.of(arraySupplier.get());
// }
// }
// };
// }
/**
* Lazy evaluation.
*
* @param iteratorSupplier
* @return
*/
public static ObjIteratorEx defer(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) {
init();
}
return iter.hasNext();
}
@Override
public T next() {
if (!isInitialized) {
init();
}
return iter.next();
}
@Override
public void advance(long n) {
if (!isInitialized) {
init();
}
if (iterEx != null) {
iterEx.advance(n);
} else {
super.advance(n);
}
}
@Override
public long count() {
if (!isInitialized) {
init();
}
if (iterEx != null) {
return iterEx.count();
} else {
return super.count();
}
}
@Override
public void close() {
if (!isInitialized) {
init();
}
if (iterEx != null) {
iterEx.close();
}
}
private void init() {
if (!isInitialized) {
isInitialized = true;
iter = iteratorSupplier.get();
iterEx = iter instanceof ObjIteratorEx ? (ObjIteratorEx) iter : null;
}
}
};
}
@Override
public void advance(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.
}
abstract static class BufferedIterator extends ObjIteratorEx {
private final int bufferSize;
BufferedIterator(int bufferSize) {
this.bufferSize = bufferSize;
}
public int max() {
return bufferSize;
}
}
}