java拓展集合工具类CollectionUtils

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;

/**
 *
 * <p>自定义集合工具类拓展常用方法</p>
 * @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;

 /**
  *
  * <p>拆分List为固定大小的多个集合</p>
  * <p>推荐使用</p>
  * <p>返回集合的size越小,此方法性能越高</p>
  * @param baseList
  * @param size
  * @return ArrayList
  * @autho 董杨炀
  * @time 2017-4-10 上午11:30:43
  */
 @SuppressWarnings("unchecked")
 public static <T> List<List<T>> fastSplitList(List<T> 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<List<T>> resultList = new ArrayList<List<T>>();
  for (int i = 0; i < arrSize; i++) {
   if (arrSize - 1 == i) {
    resultList.add((List<T>) new ArrayList<Object>( baseList.subList(i * size, baseList.size())));
   } else {
    resultList.add((List<T>) new ArrayList<Object>( baseList.subList(i * size, size * (i + 1))));
   }
  }
  return resultList;
 }

 /**
  *
  * <p>拆分List为固定大小的多个集合</p>
  * <p>返回集合的size越大,此方法性能越高</p>
  * @param baseList
  * @param size
  * @return ArrayList
  * @autho 董杨炀
  * @time 2017-4-10 上午11:30:43
  */
 public static <T> List<List<T>> splitList(List<T> baseList, int size) {
  if (baseList == null || baseList.size() == 0) {
   return null;
  }
  if (size <= 0) {
   size = DEFAULT_SIZE;
  }
  List<List<T>> resultList = new ArrayList<List<T>>();
  for (int i = 0; i < baseList.size(); ++i) {
   if (i % size == 0) {
    List<T> result = new ArrayList<T>();
    resultList.add(result);
   }
   resultList.get(i / size).add(baseList.get(i));
  }
  return resultList;
 }

 /**
  *
  * <p>集合转Set</p>
  * @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 <K, V> Set<K> asSet(final java.util.Collection<V> coll,final Class<K> keyType
   ,final String keyMethodName) {
  if (CollectionUtils.isEmpty(coll)) {
   return new HashSet<K>(0);
  }
  final Set<K> set = new LinkedHashSet<K>(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;
 }

 /**
  *
  * <p>集合转Map</p>
  * <p>比如:List<EmployeeEntity>,讲EmployeeEntity的name属性作为key,转换成Map</p>
  * @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 <K, V> Map<K, V> asMap(final java.util.Collection<V> coll,final Class<K> keyType
   ,final Class<V> valueType,final String keyMethodName) {
  if (CollectionUtils.isEmpty(coll)) {
   return new LinkedHashMap<K, V>(0);
  }
  final Map<K, V> map = new LinkedHashMap<K, V>(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;
 }

 /**
  *
  * <p>集合转List</p>
  * @param coll
  * @return ArrayList
  * @autho 董杨炀
  * @time 2017-4-10 上午11:32:56
  */
 public static <V> List<V> asList(final java.util.Collection<V> coll) {
  if (CollectionUtils.isEmpty(coll)) {
   return new ArrayList<V>(0);
  }
  final List<V> list = new ArrayList<V>();
  for (final V value : coll) {
   if (value != null) {
    list.add(value);
   }
  }
  return list;
 }

 /**
  * <p>集合<String>toString</p>
  * @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<String> collection, String split) {
  StringBuilder sb = new StringBuilder();
  if (collection != null) {
   int i = 0, size = collection.size();
   for (Iterator<String> iterator = collection.iterator(); iterator.hasNext();) {
    String str = iterator.next();
    sb.append(str);
    if (++i < size) {
     sb.append(split);
    }
   }
  }
  return sb.toString();
 }

 static class CollectionUtilsException extends RuntimeException{

  private static final long serialVersionUID = 1L;

  public CollectionUtilsException(String s) {
   super(s);
  }

  public CollectionUtilsException(String s, Throwable e) {
   super(s, e);
  }

  public CollectionUtilsException(Throwable e) {
   super(e);
  }

 }

 public static void main(String[] args) {
  List<String> baseList = new ArrayList<String>(1000000);
  for (int i = 0; i < 1000000; i++) {
   baseList.add("data:"+" i");
  }
  long currentTimeMillis1 = System.currentTimeMillis();
  List<List<String>> 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<List<String>> 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<EmployeeEntity> employeeList = new ArrayList<EmployeeEntity>();
  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<String> set = CollectionUtils.asSet(employeeList, String.class, "getName");
  for (String name : set) {
   System.out.println(name);
  }

  Map<String, EmployeeEntity> map = CollectionUtils.asMap(employeeList, String.class, EmployeeEntity.class, "getName");
  Set<String> keySet = map.keySet();
  for (String key : keySet) {
   System.out.println(key);
   System.out.println(map.get(key));
  }

  List<EmployeeEntity> list = CollectionUtils.asList(map.values());
  for (EmployeeEntity employeeEntity : list) {
   System.out.println(employeeEntity);
  }
 }
}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持服务器之家。

原文链接：https://blog.csdn.net/qq_35712358/article/details/70254565