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A general and simple library for Android
/*
* Copyright (c) 2017, 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;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import com.landawn.abacus.util.function.BooleanSupplier;
import com.landawn.abacus.util.function.Supplier;
import com.landawn.abacus.util.stream.Stream;
/**
*
* @since 0.9
*
* @author Haiyang Li
*/
public abstract class ObjIterator extends ImmutableIterator {
@SuppressWarnings("rawtypes")
private static final ObjIterator EMPTY = new ObjIterator() {
@Override
public boolean hasNext() {
return false;
}
@Override
public Object next() {
throw new NoSuchElementException();
}
};
public static ObjIterator empty() {
return EMPTY;
}
public static ObjIterator just(final T val) {
return new ObjIterator() {
private boolean done = false;
@Override
public boolean hasNext() {
return done == false;
}
@Override
public T next() {
if (done) {
throw new NoSuchElementException();
}
done = true;
return val;
}
};
}
@SafeVarargs
public static ObjIterator of(final T... a) {
return N.isNullOrEmpty(a) ? EMPTY : of(a, 0, a.length);
}
public static ObjIterator of(final T[] a, final int fromIndex, final int toIndex) {
N.checkFromToIndex(fromIndex, toIndex, a == null ? 0 : a.length);
if (fromIndex == toIndex) {
return EMPTY;
}
return new ObjIterator() {
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 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());
}
};
}
public static ObjIterator of(final Iterator iter) {
if (iter == null) {
return empty();
} else if (iter instanceof ObjIterator) {
return (ObjIterator) iter;
}
return new ObjIterator() {
@Override
public boolean hasNext() {
return iter.hasNext();
}
@Override
public T next() {
return iter.next();
}
};
}
public static ObjIterator of(final Collection iterable) {
return iterable == null ? ObjIterator. empty() : of(iterable.iterator());
}
public static ObjIterator of(final Iterable iterable) {
return iterable == null ? ObjIterator. empty() : of(iterable.iterator());
}
/**
* Lazy evaluation.
*
* @param iteratorSupplier
* @return
*/
public static ObjIterator of(final Supplier> iteratorSupplier) {
N.checkArgNotNull(iteratorSupplier, "iteratorSupplier");
return new ObjIterator() {
private Iterator iter = 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();
}
private void init() {
if (isInitialized == false) {
isInitialized = true;
iter = iteratorSupplier.get();
}
}
};
}
/**
* Lazy evaluation.
*
* @param arraySupplier
* @return
*/
public static ObjIterator oF(final Supplier arraySupplier) {
N.checkArgNotNull(arraySupplier, "arraySupplier");
return new ObjIterator() {
private T[] aar = null;
private int len = 0;
private int cur = 0;
private boolean isInitialized = false;
@Override
public boolean hasNext() {
if (isInitialized == false) {
init();
}
return cur < len;
}
@Override
public T next() {
if (isInitialized == false) {
init();
}
if (cur >= len) {
throw new NoSuchElementException();
}
return aar[cur++];
}
private void init() {
if (isInitialized == false) {
isInitialized = true;
aar = arraySupplier.get();
len = N.len(aar);
}
}
};
}
/**
* Returns an infinite {@code ObjIterator}.
*
* @param supplier
* @return
*/
public static ObjIterator generate(final Supplier supplier) {
N.checkArgNotNull(supplier);
return new ObjIterator() {
@Override
public boolean hasNext() {
return true;
}
@Override
public T next() {
return supplier.get();
}
};
}
/**
*
* @param hasNext
* @param supplier
* @return
*/
public static ObjIterator generate(final BooleanSupplier hasNext, final Supplier supplier) {
N.checkArgNotNull(hasNext);
N.checkArgNotNull(supplier);
return new ObjIterator() {
@Override
public boolean hasNext() {
return hasNext.getAsBoolean();
}
@Override
public T next() {
if (hasNext() == false) {
throw new NoSuchElementException();
}
return supplier.get();
}
};
}
public Object[] toArray() {
return toArray(N.EMPTY_OBJECT_ARRAY);
}
public A[] toArray(A[] a) {
return toList().toArray(a);
}
public List toList() {
final List list = new ArrayList<>();
while (hasNext()) {
list.add(next());
}
return list;
}
public Stream stream() {
return Stream.of(this);
}
public void foreachRemaining(Try.Consumer action) throws E {
N.checkArgNotNull(action);
while (hasNext()) {
action.accept(next());
}
}
}