Flink 常见 Iterable 转 List

痛定思痛。 2024-04-17 16:24 40阅读 0赞

1，Iterable转List

Iterable<Entity> geted = entityDao.findAll();
    List<Entity> list = Lists.newArrays();
    geted.forEach(single ->{list.add(single)});

学习了：https://blog.csdn.net/u010003051/article/details/53422741

Iterator转List

方式1：
    #Apache Commons Collections:
    import org.apache.commons.collections.IteratorUtils;
    Iterator<Element> myIterator = //some iterator
    List<Element> myList=IteratorUtils.toList(myIterator);   
     
     
    方式二：
    或者自己转换
    public static <T> List<T> copyIterator(Iterator<T> iter) {
        List<T> copy = new ArrayList<T>();
        while (iter.hasNext())
            copy.add(iter.next());
        return copy;
    }
     
    使用方式：
    List<String> list = Arrays.asList("1", "2", "3");
    Iterator<String> iter = list.iterator();
    List<String> copy = copyIterator(iter);
     
    方式3：
    #Guava
    import com.google.common.collect.Lists;
    Iterator<Element> myIterator =  //some iterator
    List<Element> myList = Lists.newArrayList(myIterator);

代码实战：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMxODY2Nzkz_size_16_color_FFFFFF_t_70][]

2，List 怎么qu

>     List<Tuple2<String, Integer>>  list = new ArrayList<>();
>     System.out.println("list = " + list);
>     input.forEach(single ->{
>         list.add(single);
>     });
>     Collections.sort(list,new Comparator<Tuple2<String, Integer>>() {
>     
>         @Override
>         public int compare(Tuple2<String, Integer> o1, Tuple2<String, Integer> o2) {
>     
>             int i = o1.f1 - o2.f1;
>             return i;
>         }
>     });
>     System.out.println("list = " + list);
>     List<Tuple2<String, Integer>> tuple2s = list.subList(0, 2);
>     
>     //treemap按照key降序排列，相同count值不覆盖
>     TreeMap<Integer, Tuple2<String, Integer>> treemap = new TreeMap<Integer, Tuple2<String, Integer>>(
>             new Comparator<Integer>() {
>     
>                 @Override
>                 public int compare(Integer y, Integer x) {
>                     return (x < y) ? -1 : 1;
>                 }
>     
>             });
>     
>     //只保留前面TopN个元素
>     
>     for (Tuple2<String, Integer> element : input) {
>         treemap.put(element.f1, element);
>         if (treemap.size() > topSize) {
>             treemap.pollLastEntry();
>         }
>     }
>     
>     
>     for (Map.Entry<Integer, Tuple2<String, Integer>> entry : treemap
>             .entrySet()) {
>         out.collect("=================\n热销图书列表:\n" + new Timestamp(System.currentTimeMillis()) + treemap.toString() + "\n===============\n");
>     }

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