org.abego.commons.lang.IterableUtil Maven / Gradle / Ivy
/*
* MIT License
*
* Copyright (c) 2020 Udo Borkowski, ([email protected])
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
package org.abego.commons.lang;
import org.abego.commons.lang.exception.MustNotInstantiateException;
import org.eclipse.jdt.annotation.NonNull;
import org.eclipse.jdt.annotation.Nullable;
import java.util.Iterator;
import java.util.Objects;
import java.util.function.Function;
import java.util.function.Predicate;
@SuppressWarnings("WeakerAccess")
public final class IterableUtil {
private static final String SEPARATOR_DEFAULT = "";
private static final String EMPTY_TEXT_DEFAULT = "";
IterableUtil() {
throw new MustNotInstantiateException();
}
@SafeVarargs
public static Iterable toIterable(T... items) {
return new VarArgsIterable<>(items);
}
/**
* Append the texts of the items, stringed together to a single
* text, to the given stringBuilder.
*
* Use textOfItem(item) as the text for an individual item.
* When an item is null use the nullValueText.
*
* Use separator to separate subsequent item texts.
*
* @param items the items those texts should be joined. Elements in
* items may be null.
* @param separator the text used to separate subsequent item texts.
* [Default: ""]
* @param emptyText the text used when items contains no item.
* [Default: ""]
* @param textOfItem textOfItem(item) returns the text of
* the given item.
* [Default: Object::toString]
* @param nullValueText the text to use as an item's text when the item is
* null.
* [Default: "null"]
*/
public static void appendTextOf(
StringBuilder stringBuilder,
Iterable items,
CharSequence separator,
String emptyText,
Function textOfItem,
CharSequence nullValueText) {
boolean addSeparator = false;
boolean isEmpty = true;
for (@Nullable T item : items) {
isEmpty = false;
// Add a separator, but not before the first item
if (addSeparator)
stringBuilder.append(separator);
else
addSeparator = true;
stringBuilder.append(item == null ? nullValueText : textOfItem.apply(item));
}
if (isEmpty)
stringBuilder.append(emptyText);
}
/**
* Return the texts of the items, stringed together to a single
* text.
*
* Use textOfItem(item) as the text for an individual item.
* When an item is null use the nullValueText.
*
* Use separator to separate subsequent item texts.
*
* @param items the items those texts should be joined. Elements in
* items may be null.
* @param separator the text used to separate subsequent item texts.
* [Default: ""]
* @param emptyText the text used when items contains no item.
* [Default: ""]
* @param textOfItem textOfItem(item) returns the text of
* the given item.
* [Default: Object::toString]
* @param nullValueText the text to use as an item's text when the item is
* null.
* [Default: "null"]
* @return the joined texts of the items
*/
public static String textOf(
Iterable items,
CharSequence separator,
String emptyText,
Function textOfItem,
CharSequence nullValueText) {
StringBuilder sb = new StringBuilder();
appendTextOf(sb, items, separator, emptyText, textOfItem, nullValueText);
return sb.toString();
}
/**
* Return the texts of the items, stringed together to a single
* text.
*
* Convenience overload of {@link #textOf(Iterable, CharSequence, String, Function, CharSequence)},
* using default values for omitted parameter.
*/
public static String textOf(Iterable items) {
return textOf(items, SEPARATOR_DEFAULT, EMPTY_TEXT_DEFAULT, Object::toString, StringUtil.NULL_STRING);
}
/**
* Return the texts of the items, stringed together to a single
* text.
*
* Convenience overload of {@link #textOf(Iterable, CharSequence, String, Function, CharSequence)},
* using default values for omitted parameter.
*/
public static String textOf(
Iterable items,
CharSequence separator) {
return textOf(items, separator, EMPTY_TEXT_DEFAULT, Object::toString, StringUtil.NULL_STRING);
}
/**
* Return the texts of the items, stringed together to a single
* text.
*
* Convenience overload of {@link #textOf(Iterable, CharSequence, String, Function, CharSequence)},
* using default values for omitted parameter.
*/
public static String textOf(
Iterable items,
CharSequence separator,
Function textOfItem) {
return textOf(items, separator, EMPTY_TEXT_DEFAULT, textOfItem, StringUtil.NULL_STRING);
}
/**
* Return the texts of the items, stringed together to a single
* text.
*
* Same as {@link IterableUtil#textOf(Iterable, CharSequence)} (preferred)
*/
public static String join(CharSequence separator, Iterable items) {
return textOf(items, separator);
}
public static boolean areEqual(
Iterable iterable1, Iterable iterable2) {
if (iterable1 == iterable2) {
return true;
}
Iterator i1 = iterable1.iterator();
Iterator i2 = iterable2.iterator();
while (i1.hasNext()) {
if (!i2.hasNext() || !Objects.equals(i1.next(), i2.next())) {
return false;
}
}
return !i2.hasNext();
}
/**
* Return the hash code value for the iterable.
*
* The hash code is defined to be the result of the
* following calculation:
*
* int hashCode = 1;
* for (Object e : iterable) {
* hashCode = 31 * hashCode + (e == null ? 0 : e.hashCode());
* }
*
*/
public static int hashCodeForIterable(Iterable iterable) {
int hashCode = 1;
for (@Nullable Object e : iterable) {
hashCode = 31 * hashCode + (e == null ? 0 : e.hashCode());
}
return hashCode;
}
public static boolean isEmpty(Iterable iterable) {
return !iterable.iterator().hasNext();
}
public static int size(Iterable iterable) {
int result = 0;
for (@SuppressWarnings("unused") Object o : iterable) {
result++;
}
return result;
}
/**
* Return iterable as a String starting with the class name and followed
* by a ", " (comma and space) separated list of the items of the
* Seq in brackets (`[...]`), each item converted using {@link String#valueOf(Object)}.
*
* This method is typically used in the "toString()" methods of concrete
* {@link Iterable} implementations.
*/
public static String toStringOfIterable(Iterable iterable) {
StringBuilder sb = new StringBuilder();
sb.append(iterable.getClass().getName());
//noinspection MagicCharacter
sb.append('[');
appendTextOf(sb, iterable, ", ", "", String::valueOf, StringUtil.NULL_STRING);
//noinspection MagicCharacter
return sb.append(']').toString();
}
@Nullable
public static T firstOrNull(Iterable iterable, Predicate predicate) {
for (T i : iterable) {
if (predicate.test(i)) {
return i;
}
}
return null;
}
private static class VarArgsIterable implements Iterable {
private final T[] array;
@SafeVarargs
public VarArgsIterable(T... items) {
this.array = items;
}
@Override
@NonNull
public Iterator iterator() {
return ArrayUtil.iterator(array);
}
}
}
© 2015 - 2025 Weber Informatics LLC | Privacy Policy