java List的相关工具类

1、

<dependency>
    <groupId>com.google.guava</groupId>
    <artifactId>guava</artifactId>
    <version>18.0</version>
</dependency>

2、java代码

package xxxxxx;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.commons.lang.StringUtils;

import com.google.common.base.Function;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.ListMultimap;

public class ListUtils {

    /**
     * list 中有一个为主键key
     * 
     * @param list
     * @param function
     * @return
     */
    public static <K, V> Map<K, V> listToMap(List<V> list, Function<V, K> function) {
        Map<K, V> map = new HashMap<K, V>();
        if (list == null)
            return map;
        for (V value : list) {
            K k = function.apply(value);
            map.put(k, value);
        }
        return map;
    }

    /**
     * list 元素转为另一个元素的list
     */
    public static <F, R> List<R> listConvert(List<F> list, Function<F, R> function) {
        List<R> listN = new ArrayList<R>();
        if (list == null)
            return listN;
        for (F value : list) {
            R r = function.apply(value);
            if (r != null)
                listN.add(r);
        }
        return listN;
    }

    /**
     * list 元素过滤另一个元素的list
     */
    public static <F> List<F> filter(List<F> list, Function<F, Boolean> function) {
        List<F> listN = new ArrayList<F>();
        if (list == null)
            return listN;
        for (F value : list) {
            Boolean r = function.apply(value);
            if (r)
                listN.add(value);
        }
        return listN;
    }

    /**
     * list 元素转为另一个元素的list并且去重,适合list数据量较小
     */
    public static <F, R> List<R> listConvertAndUnique(List<F> list, Function<F, R> function) {
        List<R> listN = new ArrayList<R>();
        if (list == null)
            return listN;
        for (F value : list) {
            R r = function.apply(value);
            if (r != null && !listN.contains(r))
                listN.add(r);
        }
        return listN;
    }

    /**
     * list 元素转为以seg分割的字符串
     */
    public static String split(List list, String seg) {
        StringBuilder sb = new StringBuilder();
        for (Object value : list) {
            sb.append(value.toString() + seg);
        }
        String t = sb.toString();
        if (t.endsWith(seg)) {
            int end = t.length() - seg.length();
            t = t.substring(0, end);
        }
        return t;
    }

    public static <V> Map<Integer, V> listToMapByHashCode(List<V> list) {
        Map<Integer, V> map = new HashMap<Integer, V>();
        for (V value : list) {
            map.put(Integer.valueOf(value.hashCode()), value);
        }
        return map;
    }
    
    public static <K, V> Map<K, V> listToMapByFunction(List<V> list,Function<V,K> function) {
        Map<K, V> map = new HashMap<K, V>();
        for (V value : list) {
            map.put(function.apply(value), value);
        }
        return map;
    }

    // list to ListMultimap
    public static <K, V> ListMultimap<K, V> listToListMultiMap(List<V> list, Function<V, K> function) {
        ListMultimap listMultimap = ArrayListMultimap.<K, V> create();
        for (V value : list) {
            listMultimap.put(function.apply(value), value);
        }
        return listMultimap;
    }

    public static <V> List<V> pageList(List<V> list, int pageIndex, int pageNum) {
        int size = list.size();
        int fromIndex = pageIndex * pageNum;
        if (fromIndex > size) {
            fromIndex = size;
        }
        int toIndex = fromIndex + pageNum;
        if (toIndex > size) {
            toIndex = size;
            return list.subList(fromIndex, toIndex);
        }

        return list.subList(fromIndex, toIndex);
    }

    public static <E> boolean isEmpty(List<E> list) {

        return list == null || list.isEmpty();
    }

    public static List<String> list(String s, String spe) {

        ArrayList<String> list = new ArrayList<>();
        if (StringUtils.isBlank(s))
            return list;
        String[] e = s.split(spe);
        for (String i : e) {
            list.add(i);
        }
        return list;

    }

    public static <T> List<T> toList(T... a) {

        if (a == null)
            return null;
        List<T> l = new ArrayList<>();
        for (T e : a) {
            l.add(e);
        }

        return l;
    }

    /**
     * 通过某个字段进行排序
     */
    public static <K, V> List<V> sortList(List<V> list) {

        return null;
    }

}

3、在需要的类中调用即可

List<UserAccountDto> maList = null; //实际不能辅助为null，应该获取一个list实例
List<TopMobileAccountVo> mavoList = ListUtils.listConvert(maList,new Function<UserAccountDto, TopMobileAccountVo>() {
    public TopMobileAccountVo apply(UserAccountDto ma) {
        TopMobileAccountVo vo = new TopMobileAccountVo();
        vo.convertPOToVO(ma);
        return vo;
    }
});