Map all the time. ..
Map<key, value> map = new HashMap()<>;
I only knew. However, there is something called LinkedHashMap </ b>!
So, how to use it.
This is the best map that keeps the order of insertion </ b>.
As a scene to use ・ I want to arrange in the order of insertion ・ Arrange in an order that humans can understand, but computers do not.
I will introduce the scene of.
This is a sample that selects and displays multiple prefectures you want to go to </ b>.
Often "To Hokkaido in the north and to Okinawa in the south" But basically, they line up from north to south. .. ..
As a list ·Hokkaido ·Miyagi Prefecture ·Tokyo ・ Osaka ・ Aichi Prefecture ·Fukuoka Prefecture To set.
Insert in order from the north as described above.
import java.util.*;
public class Main {
public static void main(String[] args) throws Exception {
//List that contains the pressed prefecture
List<String> prefectureClickedList = new ArrayList();
//List of prefectures Map
Map<String, Boolean> prefectureMap = new HashMap();
// Map<String, Boolean> prefectureMap = new LinkedHashMap();
{
//Insert from the north
prefectureMap.put("Hokkaido", false);
prefectureMap.put("Miyagi Prefecture", false);
prefectureMap.put("Tokyo", false);
prefectureMap.put("Osaka", false);
prefectureMap.put("Aichi prefecture", false);
prefectureMap.put("Fukuoka Prefecture", false);
}
//Pressing process (in different order)
prefectureMap.put("Fukuoka Prefecture", true);
prefectureMap.put("Osaka", true);
prefectureMap.put("Tokyo", true);
prefectureMap.put("Hokkaido", true);
//Add to prefectureClickedList
for(String prefecture: prefectureMap.keySet()) {
Boolean bool = prefectureMap.get(prefecture);
if(bool){
prefectureClickedList.add(prefecture);
}
}
//Output String
String outPrefecture = new String();
//Midpoint"・"Put in"
for(String clickedPref : prefectureClickedList) {
outPrefecture = outPrefecture + clickedPref + "・";
}
outPrefecture = outPrefecture.substring(0, outPrefecture.length() -1);
System.out.println("Prefecture you want to go to:" + outPrefecture);
}
}
Output result
Prefectures you want to go to: Hokkaido, Osaka, Tokyo, Fukuoka
Well, I want to change the order of Osaka and Tokyo! !! Ww
import java.util.*;
public class Main {
public static void main(String[] args) throws Exception {
//List that contains the pressed prefecture
List<String> prefectureClickedList = new ArrayList();
//List of prefectures Map
// Map<String, Boolean> prefectureMap = new HashMap();
Map<String, Boolean> prefectureMap = new LinkedHashMap();
{
//Insert from the north
prefectureMap.put("Hokkaido", false);
prefectureMap.put("Miyagi Prefecture", false);
prefectureMap.put("Tokyo", false);
prefectureMap.put("Osaka", false);
prefectureMap.put("Aichi prefecture", false);
prefectureMap.put("Fukuoka Prefecture", false);
}
//Pressing process (in different order)
prefectureMap.put("Tokyo", true);
prefectureMap.put("Fukuoka Prefecture", true);
prefectureMap.put("Osaka", true);
prefectureMap.put("Hokkaido", true);
//Add to prefectureClickedList
for(String prefecture: prefectureMap.keySet()) {
Boolean bool = prefectureMap.get(prefecture);
if(bool){
prefectureClickedList.add(prefecture);
}
}
//Output String
String outPrefecture = new String();
//Midpoint"・"Put in"
for(String clickedPref : prefectureClickedList) {
outPrefecture = outPrefecture + clickedPref + "・";
}
outPrefecture = outPrefecture.substring(0, outPrefecture.length() -1);
System.out.println("Prefecture you want to go to:" + outPrefecture);
}
}
Output result
Prefectures you want to visit: Hokkaido, Tokyo, Osaka, Fukuoka
Yup. There is no sense of discomfort.
Highest & highest!
・ Order of prefectures: North to south -Washing order: wash, rinse, dehydrate ・ Four seasons: Spring, summer, autumn, winter -Char's MS: Zaku, Z'Gok, (Rick Dom), Gelgoog, Zeong. ..
These are commonplace for humans to see at a glance.
Check the latitude and longitude of Hokkaido and the latitude and longitude of Fukuoka, and arrange them in order from the north. .. You can do it, but I was able to deal with it by putting them in predetermined order </ b>.
Why didn't I know such a wonderful Linked Hash Map? .. Because I'm a little boy </ b>