先看HashMap的定义：public class HashMap<K,V>extends AbstractMap<K,V>implements Map<K,V>, Cloneable, SerializableHashMap是AbstractMap的子类，实现了Map接口。HashMap()Constructs an empty HashMap wit
一、集合与数组数组（可以存储基本数据类型）是用来存现对象的一种容器，但是数组的长度固定，不适合在对象数量未知的情况下使用。集合（只能存储对象，对象类型可以不一样）的长度可变，可在多数情况下使用。二、层次关系Collection接口是集合类的根接口，Java中没有提供这个接口的直接的实现类。但是却让其被继承产生了两个接口，就是Set和List。Set中不能包含重复的元素。List是一个有序的集合，可
返回的串 {"took":278,"timed_out":false,"_shards":{"total":21,"successful":21,"failed":0},"hits":{"total":3,"max_score":6.685612,"hits":[{"_index":"logstash-winlogbeat-2018.11.19","_type":"wineventlog","
/*[ { "repairo": "asda", "num": 88.71 }, { "repairo": "fghfghfgh", "num": 50 }, { "repairo": "ytutyu", "num": 5.47 }, { "repairo":
一 .遍历JsonObject JSONObject jsonObject = JSONObject.fromObject(string); Iterator iterator = jsonObject.keys(); while(iterator.hasNext()){
LinkedHashSet<String> set = new LinkedHashSet<String>(arrayList.size()); set.addAll(arrayList); arrayList.clear(); arrayList.addAll(set);
import java.util.ArrayList;import java.util.HashMap;import java.util.Iterator;import java.util.List;import java.util.Map;import java.util.Map.Entry;public class CountDuplicatedList { public static voi
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