[Java] Map comparison

Map comparison method

·Thing you want to do I want to compare List A and List B and extract only those that are in both and those that are in List A. I want to change the process when updating and when new


/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
    public static void main (String[] args) throws java.lang.Exception
        // MAP-A
        Map<String, String> listA = new HashMap<String, String>();
        // MAP-B
        Map<String, String> listB = new HashMap<String, String>();

        //Set<Map.Entry<K,V>>If it is also in List B, update it, if not, new
        for(Map.Entry<String,String> entry : listA.entrySet()){
            String key = entry.getKey();
            String val = entry.getValue();
            if(listB.get(key) != null){
                entry.setValue(val + "Koshin");
            } else {
                entry.setValue(val + "Shinki");

It was actually more complicated, but when simplified, it looks like this. First, prepare list C, throw common elements into list C, delete the elements from lists A and B, and finally, if there are any elements left in list A, add them as new. I made it into a shape, but when I made a change to that element while turning it with an iterator, it seemed to be useless, and an error occurred, so I changed it. This is nice to be cleaner.

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