java拓展集合工具类CollectionUtils

2021-10-12 14:20:10分类：编程 / Java阅读(7088)评论(0)

这篇文章主要为大家详细介绍了java拓展集合工具类CollectionUtils，具有一定的参考价值，感兴趣的小伙伴们可以参考一下

拓展集合工具类CollectionUtils，供大家参考，具体内容如下

 package com.demo.utils; import java.lang.reflect.Method; import java.util.ArrayList; import java.util.Collection; import java.util.HashSet; import java.util.Iterator; import java.util.LinkedHashMap; import java.util.LinkedHashSet; import java.util.List; import java.util.Map; import java.util.Set; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import com.demo.bean.EmployeeEntity; /** * * 
自定义集合工具类拓展常用方法
 * @autho 董杨炀 * @time 2017-4-10 上午11:33:36 */ public class CollectionUtils extends org.apache.commons.collections.CollectionUtils { private static final Logger LOGGER = LoggerFactory.getLogger(CollectionUtils.class); private static final int DEFAULT_SIZE = 1000; /** * * 
拆分List为固定大小的多个集合
 * 
推荐使用
 * 
返回集合的size越小,此方法性能越高
 * @param baseList * @param size * @return ArrayList * @autho 董杨炀 * @time 2017-4-10 上午11:30:43 */ @SuppressWarnings("unchecked") public static  List> fastSplitList(List baseList, int size) { if (baseList == null || baseList.size() == 0) { return null; } if (size <= 0) { size = DEFAULT_SIZE; } int arrSize = baseList.size() % size == 0 ? baseList.size() / size : baseList.size() / size + 1; List> resultList = new ArrayList>(); for (int i = 0; i ) new ArrayList( baseList.subList(i * size, baseList.size()))); } else { resultList.add((List) new ArrayList( baseList.subList(i * size, size * (i + 1)))); } } return resultList; } /** * * 
拆分List为固定大小的多个集合
 * 
返回集合的size越大,此方法性能越高
 * @param baseList * @param size * @return ArrayList * @autho 董杨炀 * @time 2017-4-10 上午11:30:43 */ public static  List> splitList(List baseList, int size) { if (baseList == null || baseList.size() == 0) { return null; } if (size <= 0) { size = DEFAULT_SIZE; } List> resultList = new ArrayList>(); for (int i = 0; i  result = new ArrayList(); resultList.add(result); } resultList.get(i / size).add(baseList.get(i)); } return resultList; } /** * * 
集合转Set
 * @param coll 源集合 * @param keyType 属性类型 * @param keyMethodName 属性get方法 * @return LinkedHashSet * @autho 董杨炀 * @time 2017-4-10 上午11:31:50 */ public static  Set asSet(final java.util.Collection coll,final Class keyType ,final String keyMethodName) { if (CollectionUtils.isEmpty(coll)) { return new HashSet(0); } final Set set = new LinkedHashSet(coll.size()); try { for (final V value : coll) { Object object; Method method = value.getClass().getMethod(keyMethodName); object = method.invoke(value); @SuppressWarnings("unchecked") final K key = (K) object; set.add(key); } } catch (Exception e) { LOGGER.error(e.getMessage(), e); throw new CollectionUtilsException("Collection conversion Set exceptions"); } return set; } /** * * 
集合转Map
 * 
比如:List,讲EmployeeEntity的name属性作为key,转换成Map
 * @param coll 源集合 * @param keyType 属性类型 * @param valueType 源数据类型(实体类型) * @param keyMethodName 属性get方法 * @return LinkedHashMap * @autho 董杨炀 * @time 2017-4-10 上午11:32:01 */ public static  Map asMap(final java.util.Collection coll,final Class keyType ,final Class valueType,final String keyMethodName) { if (CollectionUtils.isEmpty(coll)) { return new LinkedHashMap(0); } final Map map = new LinkedHashMap(coll.size()); try { Method method = valueType.getMethod(keyMethodName); for (final V value : coll) { Object object; object = method.invoke(value); @SuppressWarnings("unchecked") final K key = (K) object; map.put(key, value); } } catch (Exception e) { LOGGER.error(e.getMessage(), e); throw new CollectionUtilsException("Collection conversion Map exceptions"); } return map; } /** * * 
集合转List
 * @param coll * @return ArrayList * @autho 董杨炀 * @time 2017-4-10 上午11:32:56 */ public static  List asList(final java.util.Collection coll) { if (CollectionUtils.isEmpty(coll)) { return new ArrayList(0); } final List list = new ArrayList(); for (final V value : coll) { if (value != null) { list.add(value); } } return list; } /** * 
集合toString
 * @param collection 泛型必须为String类型 * @param split 比如连接符"," * @return * @autho 董杨炀 * @time 2017-4-10 下午3:22:24 */ public static String collToString(Collection collection, String split) { StringBuilder sb = new StringBuilder(); if (collection != null) { int i = 0, size = collection.size(); for (Iterator iterator = collection.iterator(); iterator.hasNext();) { String str = iterator.next(); sb.append(str); if (++i  baseList = new ArrayList(1000000); for (int i = 0; i <1000000; i++) { baseList.add("data:"+" i"); } long currentTimeMillis1 = System.currentTimeMillis(); List> splitList = splitList(baseList, 1000); long currentTimeMillis2 = System.currentTimeMillis(); System.out.println(splitList.size()); System.out.println("切割完成时间为:"+String.valueOf(currentTimeMillis2-currentTimeMillis1)+"毫秒"); long currentTimeMillis3 = System.currentTimeMillis(); List> newList = fastSplitList(baseList,1000); long currentTimeMillis4 = System.currentTimeMillis(); System.out.println(newList.size()); System.out.println("快速切割完成时间为:"+String.valueOf(currentTimeMillis4-currentTimeMillis3)+"毫秒"); List employeeList = new ArrayList(); for (int i = 1; i <11; i++) { EmployeeEntity entity = new EmployeeEntity(); entity.setName("名字"+String.valueOf(i)); employeeList.add(entity); } System.out.println(employeeList.size()); Set set = CollectionUtils.asSet(employeeList, String.class, "getName"); for (String name : set) { System.out.println(name); } Map map = CollectionUtils.asMap(employeeList, String.class, EmployeeEntity.class, "getName"); Set keySet = map.keySet(); for (String key : keySet) { System.out.println(key); System.out.println(map.get(key)); } List list = CollectionUtils.asList(map.values()); for (EmployeeEntity employeeEntity : list) { System.out.println(employeeEntity); } } } 
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