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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) 2020, 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.Enumeration;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.function.Supplier;
public final class Enumerations {
@SuppressWarnings("rawtypes")
private static final Enumeration EMPTY = new Enumeration() {
@Override
public boolean hasMoreElements() {
return false;
}
@Override
public Object nextElement() {
throw new NoSuchElementException();
}
};
private Enumerations() {
// singleton
}
/**
*
*
* @param
* @return
*/
public static Enumeration empty() {
return EMPTY;
}
/**
*
*
* @param
* @param single
* @return
*/
public static Enumeration just(final T single) {
return new Enumeration<>() {
private boolean hasNext = true;
@Override
public boolean hasMoreElements() {
return hasNext;
}
@Override
public T nextElement() {
if (!hasNext) {
throw new NoSuchElementException();
}
hasNext = false;
return single;
}
};
}
/**
*
*
* @param
* @param a
* @return
*/
public static Enumeration of(final T... a) {
if (N.isNullOrEmpty(a)) {
return empty();
}
return new Enumeration<>() {
private final int len = a.length;
private int cursor = 0;
@Override
public boolean hasMoreElements() {
return cursor < len;
}
@Override
public T nextElement() {
if (cursor >= len) {
throw new NoSuchElementException();
}
return a[cursor++];
}
};
}
/**
*
*
* @param
* @param c
* @return
*/
public static Enumeration from(final Collection c) {
if (N.isNullOrEmpty(c)) {
return empty();
}
return from(c.iterator());
}
/**
*
*
* @param
* @param iter
* @return
*/
public static Enumeration from(final Iterator iter) {
return new Enumeration<>() {
@Override
public boolean hasMoreElements() {
return iter.hasNext();
}
@Override
public T nextElement() {
return iter.next();
}
};
}
/**
*
* @param
* @param a
* @return
*/
@SafeVarargs
public static Enumeration concat(final Enumeration... a) {
if (N.isNullOrEmpty(a)) {
return empty();
}
return concat(Array.asList(a));
}
/**
*
* @param
* @param c
* @return
*/
public static Enumeration concat(final Collection> c) {
if (N.isNullOrEmpty(c)) {
return empty();
}
return new Enumeration<>() {
private final Iterator> iter = c.iterator();
private Enumeration cur;
@Override
public boolean hasMoreElements() {
while ((cur == null || !cur.hasMoreElements()) && iter.hasNext()) {
cur = iter.next();
}
return cur != null && cur.hasMoreElements();
}
@Override
public T nextElement() {
if ((cur == null || !cur.hasMoreElements()) && !hasMoreElements()) {
throw new NoSuchElementException();
}
return cur.nextElement();
}
};
}
/**
*
*
* @param
* @param e
* @return
*/
public static ObjIterator toIterator(final Enumeration e) {
if (e == null) {
return ObjIterator.empty();
}
return new ObjIterator<>() {
@Override
public boolean hasNext() {
return e.hasMoreElements();
}
@Override
public T next() {
return e.nextElement();
}
};
}
/**
*
*
* @param
* @param e
* @return
*/
public static List toList(final Enumeration e) {
if (e == null) {
return new ArrayList<>();
}
final List result = new ArrayList<>();
while (e.hasMoreElements()) {
result.add(e.nextElement());
}
return result;
}
/**
*
*
* @param
* @param e
* @return
*/
public static Set toSet(final Enumeration e) {
if (e == null) {
return new HashSet<>();
}
final Set result = new HashSet<>();
while (e.hasMoreElements()) {
result.add(e.nextElement());
}
return result;
}
/**
*
*
* @param
* @param
* @param e
* @param supplier
* @return
*/
public static > C toCollection(final Enumeration e, final Supplier supplier) {
final C c = supplier.get();
if (e != null) {
while (e.hasMoreElements()) {
c.add(e.nextElement());
}
}
return c;
}
}