hashmap | 易学教程

OnClickItem() in gridView how do I show the same image in a separate imageView

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问题 The GridView is already being populated by the contents of a specific folder called "MyDir". My layout gallery_fragment is split in half by two linearlayouts. The one on the left has the GridView which is already populated with the images from "MyDir". The layout on the right has an ImageView. The idea is that I can select an image from the GridView on the left and then it will appear on the ImageView on the right. I cannot use the res/drawables folder in this instance. I have been told I

浅谈HashMap

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目录浅谈HashMap 基本特性定义历遍 HashMap的模型初始化 Get和Put方法浅谈HashMap 基本特性定义 hashMap是一个无序的，非空的容器，而且是非同步的容器会造成线程不安全的这类问题，即有许多人都想要同一份学习资料，系统会复制出多份资料后，给每个人一份资料，而不同的人对这份资料有着不同的看法并对该资料进行修改，再上传到系统中。可想而知资料会有多少个版本，但是系统只能存放一个版本的资料，因而会丢失大量版本信息。线程不安全：简单来说，就是用户读到的信息有一定可能是错误的，从而做出错误的操作（抢票时，可能抢到重票或抢到一张不存在的票）历遍 HashMap的容量太大或太小，不利于literation（迭代器）查询目标。 HashMap的模型 HashMap是数组和单向列表的结合体，即用数组来装列表的表头，因此在做增删等操作时，所消耗的时间和空间会比数组小，查询容器的中元素的速度会比列表快。类似于下图初始化 HashMash中常量： HashMap有4个构造函数; public HashMap() { this.loadFactor = DEFAULT_LOAD_FACTOR; //使用默认的加速因子，bucket 的大小为默认的16 } 1 public HashMap(int initialCapacity, float loadFactor) {

使用QueryDSL补充springDataJpa进行复杂动态sql语句进行sql查询实现关联分页等功能

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@Test public void testComplexSelect() { QQyOnlineCall onlineCall = QQyOnlineCall.qyOnlineCall; QClientList clientList = QClientList.clientList; // page必须从1开始 PageRequest request = PageRequest.of(0, 10); // 构建复杂查询语句 List<Tuple> result = mFactory.select(onlineCall.id, onlineCall.cUsesign, onlineCall.cYgscode, clientList.cClientname, clientList.cPhone1) .from(onlineCall) .leftJoin(clientList) .on(onlineCall.cClientid.eq(clientList.id)) .where(onlineCall.cCom.eq("C0003")) .limit(request.getPageSize()) // 单页查询数量 .offset(request.getPageSize() * request.getPageNumber()) // 偏移量 .fetch(); // 获取结果 for

HashMap De-Serialization

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问题 I have a server/client app where I retrieve data from the server via Hessian/hessdroid. The data is very complex with HashMaps containing other HashMaps and images stored in byte arrays. I can display the data perfectly. To not always query the server, I´m using a data structure as a cache. This data object I save to SD card using ObjectOutputStream when closing the app. When I restart it, I read it back to memory with an ObjectInputStream. I´m having problems with the app only after reading

filter Map in Java 8 Streams

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问题 I was trying to filter Entries in HashMap using Streams API, but stuck in last method call Collectors.toMap . So, I don't have clue to implemement toMap method public void filterStudents(Map<Integer, Student> studentsMap){ HashMap<Integer, Student> filteredStudentsMap = studentsMap.entrySet().stream(). filter(s -> s.getValue().getAddress().equalsIgnoreCase("delhi")). collect(Collectors.toMap(k , v)); } public class Student { private int id; private String firstName; private String lastName;

Java key - key map

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问题 I need a kind of map which is accessible in two directions, so with a key-key structure instead of key-value. Does this exist in Java? If not, what is the best way to create it? So example: mySpecialHashMap.put("key1", "key2"); mySpecialMap.getL2R("key1") returns "key2"; mySpecialMap.getR2L("key2") returns "key1"; 回答1: So you want a bidirectional map. You can use Apache Commons Collections BidiMap or Google Collections BiMap for this. 回答2: You might want to look at BiMap from the Guava

How to set a value in an unordered_map and find out if a new key was added

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问题 How can I efficiently and idiomatically set a value in an unordered_map and find out if a new key was added: #include <unordered_map> #include <string> int main() { auto map = std::unordered_map<std::string, int>{{"foo", 1}, {"bar", 2}}; map["foo"] = 3; // how to find out if a new key was added? } I can't use insert() directly because I want to overwrite the value if there is one already and insert does not do that. I can't use operator[] directly because it provides no information about

HashMap分析

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HashMap分析 HashMap是常用容器。以下展示一些用法 import java . util . HashMap ; import java . util . Map ; public class HashMapTest { public static void main ( String [ ] args ) { Map < String , String > map = new HashMap < > ( ) ; map . put ( "name" , "zhangsan" ) ; String name = map . get ( "name" ) ; } } HaseMap的数据结构是链表数组。 transient Node < K , V > [ ] table ; static class Node < K , V > implements Map . Entry < K , V > { final int hash ; final K key ; V value ; Node < K , V > next ; Node ( int hash , K key , V value , Node < K , V > next ) { this . hash = hash ; this . key = key ; this . value = value ;

Druid数据源配置多个数据库

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言简意赅 pom.xml文件引入jar包 < ! -- jdbc连接数据库 -- > < dependency > < groupId > org . springframework . boot < / groupId > < artifactId > spring - boot - starter - jdbc < / artifactId > < / dependency > < ! -- mysql -- > < dependency > < groupId > mysql < / groupId > < artifactId > mysql - connector - java < / artifactId > < / dependency > < dependency > < groupId > com . alibaba < / groupId > < artifactId > druid < / artifactId > < version > 1.1 .16 < / version > < / dependency > application.properties # # # #配置多个数据库 : 用户信息存储数据库 : xcn_admin_database xcn_admin_database . druid . url = jdbc : mysql : / /

ANSI C hash table implementation with data in one memory block

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问题 I am looking for an open source C implementation of a hash table that keeps all the data in one memory block, so it can be easily send over a network let say. I can only find ones that allocate small pieces of memory for every key-value pair added to it. Thank you very much in advance for all the inputs. EDIT: It doesn't necessarily need to be a hash table, whatever key-value pair table would probably do. 回答1: On a unix system I'd probably utilise a shared memory buffer (see shm_open()), or