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import cn.sh.ideal.bean.UserBean;import java.util.*;import java.util.function.Function;import java.util.stream.Collectors;import java.util.stream.Stream;/** * Lambda表达式写法 * * @author gilbert */public class LambdaDemo {    /**     * 功能描述 无参无返回值     *     * @param list     * @return void     * @author gilbert     * @date 2019/6/12     */    public static void lambdaWithParamAndNoReturn(List
   
     list) {        list.forEach(userBean -> System.out.println("hello," + userBean.getUsername()));    }    /**     *功能描述 重新封装集合数据     * @author gilbert     * @date 2019/6/12     * @param [list]     * @return void     */    public static void initList(List
    
      list){        List
     
       userList = list.stream().map(userBean -> new UserBean(userBean.getUserid(), userBean.getWorkid(), userBean.getUsername())).collect(Collectors.toList());        userList.forEach(userBean -> System.out.println("new list:" + userBean.getUsername()));    }    /**     *功能描述 集合过滤     * @author gilbert     * @date 2019/6/12     * @param [list]     * @return void     */    public static void filterList(List
      
        list){        //List
       
         filterList = list.stream().filter(userBean -> userBean.getUsername().contains("g")).collect(Collectors.toList());        List
        
          filterList = list.stream().filter(userBean -> Integer.valueOf(userBean.getUserid()) > 6).collect(Collectors.toList()); filterList.forEach(userBean -> System.out.println("filter list:" + userBean.getUsername())); } /** *功能描述 排序 * @author gilbert * @date 2019/6/12 * @param [list] * @return void */ public static void sortList(List
         
           list){ //按userid排序 List
          
            sortList = list.stream().sorted((userBean1,userBean2) -> userBean1.getUsername().compareTo(userBean2.getUsername())).collect(Collectors.toList()); sortList.forEach(userBean -> System.out.println("sortList:" + userBean.getUserid() + "," + userBean.getUsername())); } /** *功能描述 多条件排序 * @author gilbert * @date 2019/6/12 * @param [list] * @return void */ public static void multiSortList(List
           
             list){ list.sort(Comparator.comparing(UserBean::getUserid).thenComparing(UserBean::getUsername)); list.forEach(userBean -> System.out.println("multiSortList:" + userBean.getUserid() + "," + userBean.getUsername())); } /** *功能描述 倒序 * @author gilbert * @date 2019/6/12 * @param [list] * @return void */ public static void reversedSortList(List
            
              list){ //第一种写法 Comparator
             
               comparator = (userBean1,userBean2) -> userBean1.getUsername().compareTo(userBean2.getUsername()); list.sort(comparator.reversed()); //第二种写法 //list.sort(Comparator.comparing(UserBean::getUserid).reversed()); list.forEach(userBean -> System.out.println("reverseSortList:" + userBean.getUserid() + "," + userBean.getUsername())); } /** *功能描述 多条件倒序 * @author gilbert * @date 2019/6/12 * @param [list] * @return void */ public static void multiReversedSortList(List
              
                list){ list.sort(Comparator.comparing(UserBean::getUserid).thenComparing(UserBean::getUsername).reversed()); list.forEach(userBean -> System.out.println("multiReversedSortList:" + userBean.getUserid() + "," + userBean.getUsername())); } /** *功能描述 集合分组 * @author gilbert * @date 2019/6/12 * @param [list] * @return void */ public static void groupByList(List
               
                 list){ Map
                
                 
                  > groupByMap = list.stream().collect(Collectors.groupingBy(UserBean::getWorkid)); groupByMap.forEach((k,v) -> System.out.println(k+"," + v)); } /** *功能描述 求和 * @author gilbert * @date 2019/6/12 * @param [list] * @return void */ public static void sumByList(List
                  
                    list){ System.out.println("sum="+ list.stream().mapToInt(UserBean::getUserid).sum()); } /** *功能描述 最大值 * @author gilbert * @date 2019/6/12 * @param [list] * @return void */ public static void maxByList(List
                   
                     list){ OptionalInt optional = list.stream().mapToInt(UserBean::getUserid).max(); System.out.println("max=" + optional.getAsInt()); } /** *功能描述 最小值 * @author gilbert * @date 2019/6/12 * @param [list] * @return void */ public static void minByList(List
                    
                      list){ OptionalInt optional = list.stream().mapToInt(UserBean::getUserid).min(); System.out.println("min=" + optional.getAsInt()); } /** *功能描述 平均值 * @author gilbert * @date 2019/6/12 * @param [list] * @return void */ public static void averageByList(List
                     
                       list){ OptionalDouble optionalDouble = list.stream().mapToInt(UserBean::getUserid).average(); System.out.println("average=" + optionalDouble.getAsDouble()); } /** *功能描述 List转map * @author gilbert * @date 2019/6/12 * @param [list] * @return void */ public static void listToMap(List
                      
                        list){ //用 (k1,k2)->k1 来设置，如果有重复的key,则保留key1,舍弃key2 Map
                       
                         map = list.stream().collect(Collectors.toMap(UserBean::getUserid,userBean -> userBean, (k1, k2) -> k1)); map.forEach((k,v) -> System.out.println("k=" + k + ",v=" + v)); } /** *功能描述 map转list * @author gilbert * @date 2019/6/12 * @param [map] * @return void */ public static void mapToList(Map
                        
                          map){ List
                         
                           list = map.entrySet().stream().sorted(Comparator.comparing(key -> key.getKey())).map(key -> new UserBean(Integer.valueOf(key.getKey()),key.getValue(),key.getValue())).collect(Collectors.toList()); list.forEach(userBean -> System.out.println(userBean.getUserid() + "," + userBean.getUsername())); } /** *功能描述 字符串转list * @author gilbert * @date 2019/6/12 * @param [str] * @return void */ public static void stringToList(String str){ //不需要处理 //
                          
                            list = Arrays.asList(str.split(",")); //需要处理 List
                           
                             list = Arrays.asList(str.split(",")).stream().map(string -> String.valueOf(string)).collect(Collectors.toList()); list.forEach(string -> System.out.println(string)); } /** *功能描述 姓名以逗号拼接 * @author gilbert * @date 2019/6/12 * @param [list] * @return void */ public static void joinStringValueByList(List
                            
                              list){ System.out.println(list.stream().map(UserBean::getUsername).collect(Collectors.joining(","))); } /** *功能描述 分组统计 * @author gilbert * @date 2019/6/12 * @param [list] * @return void */ public static void countByList(List
                             
                               list){ Map
                              
                                map = list.stream().collect(Collectors.groupingBy(UserBean::getWorkid,Collectors.counting())); map.forEach((k,v) -> System.out.println("key=" + k + ",value=" + v)); } public static void main(String[] args) { //List
                               
                                 list = Arrays.asList(new UserBean(1, "AKB001", "gilbert"), new UserBean("2", "AKB002", "apple"), new UserBean("3", "AKB003", "cat")); List
                                
                                  list = Stream.of(new UserBean(1, "AKB001", "gilbert"), new UserBean(2, "AKB002", "apple"), new UserBean(4, "AKB004", "dog"), new UserBean(5, "AKB005", "egg"), new UserBean(6, "AKB006", "frog"), new UserBean(6, "AKB006", "banana"), new UserBean(7, "AKB007", "google"), new UserBean(3, "AKB003", "cat")) .collect(Collectors.toList()); lambdaWithParamAndNoReturn(list); initList(list); filterList(list); sortList(list); reversedSortList(list); multiSortList(list); multiReversedSortList(list); groupByList(list); sumByList(list); maxByList(list); minByList(list); averageByList(list); listToMap(list); String str = "apple,banana,cat,dog"; stringToList(str); Map
                                 
                                   map =new HashMap
                                  
                                   () { { put(1, "apple"); put(2, "banana"); put(3, "cat"); put(4, "dog"); put(5, "frog"); } }; mapToList(map); joinStringValueByList(list); countByList(list); }}
                                  
                                 
                                
                               
                              
                             
                            
                           
                          
                         
                        
                       
                      
                     
                    
                   
                  
                 
                
               
              
             
            
           
          
         
        
       
      
     
    
   

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