/*
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* Copyright 2002-2010 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.walker.infrastructure.utils;
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import java.util.Arrays;
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import java.util.Collection;
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import java.util.Collections;
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import java.util.Enumeration;
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import java.util.Iterator;
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import java.util.List;
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import java.util.Map;
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import java.util.Properties;
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import java.util.Random;
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/**
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* Miscellaneous collection utility methods.
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* Mainly for internal use within the framework.
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*
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* @author Juergen Hoeller
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* @author Rob Harrop
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* @since 1.1.3
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*
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* @author 时克英
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* @date 2023-01-12
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*/
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public abstract class CollectionUtils {
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/**
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* 小规模抖动，
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* @param data 原始集合
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* @param weight 权重，0-100，数值越大抖动越多
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* @date 2023-01-09
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*/
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public static void shuffleLittle(List<?> data, int weight){
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if(data == null || data.size() == 0 || data.size() < 3){
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return;
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}
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if(weight <= 0){
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// 不抖动
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return;
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}
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if(weight > 100){
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// 如果设置过大，则固定为100，意思，最大限度抖动。
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weight = 100;
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Collections.shuffle(data);
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return;
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}
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float randomRate = weight / 100.0f;
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float randomSize = data.size() * randomRate;
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int shuffleSize = 0;
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if(randomSize < 1 && randomSize >= 0.5){
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// 数据量太小，不抖动
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shuffleSize = 1;
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} else {
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shuffleSize = (int)randomSize;
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}
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System.out.println("shuffleSize = " + shuffleSize);
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Random random = new Random();
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// for(int i=shuffleSize; i>1; i--){
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// int j = random.nextInt(i);
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// System.out.println("j = " + j);
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// int index = i - 1;
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// Collections.swap(data, index, j);
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// }
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int count = 0;
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for (int i = data.size(); i > 1; i--) {
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if(count >= shuffleSize){
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return;
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}
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int j = random.nextInt(i);
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int index = i - 1;
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Collections.swap(data, index, j);
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count ++;
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}
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}
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public static void shuffle(List<?> data){
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Collections.shuffle(data);
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}
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/**
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* Return <code>true</code> if the supplied Collection is <code>null</code>
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* or empty. Otherwise, return <code>false</code>.
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* @param collection the Collection to check
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* @return whether the given Collection is empty
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*/
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public static boolean isEmpty(Collection<?> collection) {
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return (collection == null || collection.isEmpty());
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}
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/**
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* Return <code>true</code> if the supplied Map is <code>null</code>
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* or empty. Otherwise, return <code>false</code>.
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* @param map the Map to check
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* @return whether the given Map is empty
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*/
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public static boolean isEmpty(Map<?,?> map) {
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return (map == null || map.isEmpty());
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}
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/**
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* Convert the supplied array into a List. A primitive array gets
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* converted into a List of the appropriate wrapper type.
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* <p>A <code>null</code> source value will be converted to an
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* empty List.
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* @param source the (potentially primitive) array
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* @return the converted List result
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* @see ObjectUtils#toObjectArray(Object)
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*/
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public static List arrayToList(Object source) {
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return Arrays.asList(ObjectUtils.toObjectArray(source));
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}
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/**
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* Merge the given array into the given Collection.
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* @param array the array to merge (may be <code>null</code>)
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* @param collection the target Collection to merge the array into
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*/
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@SuppressWarnings("unchecked")
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public static void mergeArrayIntoCollection(Object array, Collection collection) {
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if (collection == null) {
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throw new IllegalArgumentException("Collection must not be null");
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}
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Object[] arr = ObjectUtils.toObjectArray(array);
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for (Object elem : arr) {
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collection.add(elem);
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}
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}
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/**
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* Merge the given Properties instance into the given Map,
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* copying all properties (key-value pairs) over.
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* <p>Uses <code>Properties.propertyNames()</code> to even catch
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* default properties linked into the original Properties instance.
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* @param props the Properties instance to merge (may be <code>null</code>)
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* @param map the target Map to merge the properties into
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*/
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@SuppressWarnings("unchecked")
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public static void mergePropertiesIntoMap(Properties props, Map map) {
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if (map == null) {
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throw new IllegalArgumentException("Map must not be null");
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}
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if (props != null) {
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for (Enumeration en = props.propertyNames(); en.hasMoreElements();) {
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String key = (String) en.nextElement();
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Object value = props.getProperty(key);
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if (value == null) {
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// Potentially a non-String value...
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value = props.get(key);
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}
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map.put(key, value);
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}
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}
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}
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/**
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* Check whether the given Iterator contains the given element.
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* @param iterator the Iterator to check
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* @param element the element to look for
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* @return <code>true</code> if found, <code>false</code> else
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*/
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public static boolean contains(Iterator iterator, Object element) {
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if (iterator != null) {
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while (iterator.hasNext()) {
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Object candidate = iterator.next();
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if (ObjectUtils.nullSafeEquals(candidate, element)) {
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return true;
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}
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}
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}
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return false;
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}
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/**
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* Check whether the given Enumeration contains the given element.
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* @param enumeration the Enumeration to check
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* @param element the element to look for
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* @return <code>true</code> if found, <code>false</code> else
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*/
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public static boolean contains(Enumeration enumeration, Object element) {
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if (enumeration != null) {
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while (enumeration.hasMoreElements()) {
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Object candidate = enumeration.nextElement();
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if (ObjectUtils.nullSafeEquals(candidate, element)) {
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return true;
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}
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}
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}
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return false;
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}
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/**
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* Check whether the given Collection contains the given element instance.
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* <p>Enforces the given instance to be present, rather than returning
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* <code>true</code> for an equal element as well.
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* @param collection the Collection to check
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* @param element the element to look for
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* @return <code>true</code> if found, <code>false</code> else
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*/
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public static boolean containsInstance(Collection collection, Object element) {
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if (collection != null) {
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for (Object candidate : collection) {
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if (candidate == element) {
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return true;
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}
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}
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}
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return false;
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}
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/**
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* Return <code>true</code> if any element in '<code>candidates</code>' is
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* contained in '<code>source</code>'; otherwise returns <code>false</code>.
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* @param source the source Collection
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* @param candidates the candidates to search for
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* @return whether any of the candidates has been found
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*/
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public static boolean containsAny(Collection source, Collection candidates) {
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if (isEmpty(source) || isEmpty(candidates)) {
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return false;
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}
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for (Object candidate : candidates) {
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if (source.contains(candidate)) {
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return true;
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}
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}
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return false;
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}
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/**
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* Return the first element in '<code>candidates</code>' that is contained in
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* '<code>source</code>'. If no element in '<code>candidates</code>' is present in
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* '<code>source</code>' returns <code>null</code>. Iteration order is
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* {@link Collection} implementation specific.
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* @param source the source Collection
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* @param candidates the candidates to search for
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* @return the first present object, or <code>null</code> if not found
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*/
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public static Object findFirstMatch(Collection source, Collection candidates) {
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if (isEmpty(source) || isEmpty(candidates)) {
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return null;
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}
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for (Object candidate : candidates) {
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if (source.contains(candidate)) {
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return candidate;
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}
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}
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return null;
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}
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/**
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* Find a single value of the given type in the given Collection.
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* @param collection the Collection to search
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* @param type the type to look for
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* @return a value of the given type found if there is a clear match,
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* or <code>null</code> if none or more than one such value found
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*/
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@SuppressWarnings("unchecked")
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public static <T> T findValueOfType(Collection<?> collection, Class<T> type) {
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if (isEmpty(collection)) {
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return null;
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}
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T value = null;
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for (Object element : collection) {
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if (type == null || type.isInstance(element)) {
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if (value != null) {
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// More than one value found... no clear single value.
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return null;
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}
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value = (T) element;
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}
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}
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return value;
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}
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/**
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* Find a single value of one of the given types in the given Collection:
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* searching the Collection for a value of the first type, then
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* searching for a value of the second type, etc.
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* @param collection the collection to search
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* @param types the types to look for, in prioritized order
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* @return a value of one of the given types found if there is a clear match,
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* or <code>null</code> if none or more than one such value found
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*/
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public static Object findValueOfType(Collection<?> collection, Class<?>[] types) {
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if (isEmpty(collection) || ObjectUtils.isEmpty(types)) {
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return null;
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}
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for (Class<?> type : types) {
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Object value = findValueOfType(collection, type);
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if (value != null) {
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return value;
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}
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}
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return null;
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}
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/**
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* Determine whether the given Collection only contains a single unique object.
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* @param collection the Collection to check
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* @return <code>true</code> if the collection contains a single reference or
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* multiple references to the same instance, <code>false</code> else
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*/
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public static boolean hasUniqueObject(Collection collection) {
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if (isEmpty(collection)) {
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return false;
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}
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boolean hasCandidate = false;
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Object candidate = null;
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for (Object elem : collection) {
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if (!hasCandidate) {
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hasCandidate = true;
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candidate = elem;
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}
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else if (candidate != elem) {
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return false;
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}
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}
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return true;
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}
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/**
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* Find the common element type of the given Collection, if any.
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* @param collection the Collection to check
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* @return the common element type, or <code>null</code> if no clear
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* common type has been found (or the collection was empty)
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*/
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public static Class<?> findCommonElementType(Collection collection) {
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if (isEmpty(collection)) {
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return null;
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}
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Class<?> candidate = null;
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for (Object val : collection) {
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if (val != null) {
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if (candidate == null) {
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candidate = val.getClass();
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}
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else if (candidate != val.getClass()) {
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return null;
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}
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}
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}
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return candidate;
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}
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/**
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* Adapts an enumeration to an iterator.
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* @param enumeration the enumeration
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* @return the iterator
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*/
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public static <E> Iterator<E> toIterator(Enumeration<E> enumeration) {
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return new EnumerationIterator<E>(enumeration);
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}
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/**
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* Iterator wrapping an Enumeration.
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*/
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private static class EnumerationIterator<E> implements Iterator<E> {
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private Enumeration<E> enumeration;
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public EnumerationIterator(Enumeration<E> enumeration) {
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this.enumeration = enumeration;
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}
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public boolean hasNext() {
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return this.enumeration.hasMoreElements();
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}
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public E next() {
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return this.enumeration.nextElement();
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}
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public void remove() throws UnsupportedOperationException {
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throw new UnsupportedOperationException("Not supported");
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}
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}
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}
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