Starting with Java 8, we can convert aListinto aMapusing streams andCollectors: publicMap<Integer, Animal>convertListAfterJava8(List<Animal> list){ Map<Integer, Animal> map = list.stream() .collect(Collectors.toMap(Animal::getId, Function.identity()));returnmap; }Copy Again, let’s make s...
1. List to Map – Collectors.toMap() package com.mkyong.java8 import java.util.ArrayList; import java.util.List; import java.util.Map; import java.util.stream.Collectors; public class TestListMap { public static void main(String[] args) { List<Hosting> list = new ArrayList<>(); list....
Map<Integer,Employee>employeeMap=newHashMap<>();for(Employeeemployee:uniqueEmployeeList){employeeMap.put(employee.id(),employee);} Instead of unique employees list if we use the list containing duplicate employees, then theold value will be replaced by the new value for that keyin the createdM...
Map<String, Integer> userAges =users.stream().collect(Collectors.toMap(User::getUsername, User::getAge)); Set<Map.Entry<String, Integer>> entries =userAges.entrySet(); entries.forEach(entry->{ System.out.println(entry.getKey()+ ":" +entry.getValue()); });/*** 重复key*/Map<Intege...
Example 2: Convert Map to List using stream import java.util.*; import java.util.stream.Collectors; public class MapList { public static void main(String[] args) { Map<Integer, String> map = new HashMap<>(); map.put(1, "a"); map.put(2, "b"); map.put(3, "c"); map.put(...
// Java 8, seem a bit long, but you can enjoy the Stream features like filter and etc. List<String> result5 = map.values().stream() .filter(x -> !"apple".equalsIgnoreCase(x)) .collect(Collectors.toList()); // Java 8, split a map into 2 List, it works!
1.java8 .stream().xx().collect()用法 (java 8) public static void main(String[] args) { class Person { private String name; private int age; } class Person1 { private String name; } List<Person> list = new ArrayList<>();
map() method in java 8 stream is used to convert an object of one type to an object of another type or to transform elements of a collection. map() returns a stream which can be converted to an individual object or a collection, such as a list....
Likewise, we canconvert Map keys to Listusing plain Java and Streams. List<String>keyList=newArrayList<>(map.keySet());//ArrayList ConstructorList<String>listOfKeys=map.keySet().stream().collect(Collectors.toCollection(ArrayList::new));//Streams ...
(originList,charNameMap,AccountIpRecord::getCharid,AccountIpRecord::setCharName);// 提取唯一的客户端IPList<String>ipList=originList.stream().map(AccountIpRecord::getClientIp).distinct().collect(Collectors.toList());// 获取IP地区映射Map<String,String>ipRegionMap=Ip2AddressForJar.getContryCity...