JavaのSteam APIを使ってみた

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class HelloWorld {
    public static void main(String[] args) {

        List<Map<String, String>> msgList = new ArrayList<>();
        
        Map<String, String> msgMap = new HashMap<>();

        msgMap.put("1", "test[warning_726]");
        msgList.add(msgMap);

        msgMap = new HashMap<>();
        msgMap.put("1", "test3333[warning_727]");
        msgList.add(msgMap);

        msgMap = new HashMap<>();
        msgMap.put("1","test2[warning_736]");
        msgList.add(msgMap);

        msgMap = new HashMap<>();
        msgMap.put("1","test21[914_warning]");
        msgList.add(msgMap);

        msgMap = new HashMap<>();
        msgMap.put("1","test255[warning_737]");
        msgList.add(msgMap);

        msgMap = new HashMap<>();
        msgMap.put("2","error_728");
        msgList.add(msgMap);

        // msgList: [{1=test[warning_726]}, {1=test3333[warning_727]}, {1=test2[warning_736]}, {1=test21[914_warning]}, {1=test255[warning_737]}, {2=error_728}]
        System.out.println("msgList: " + msgList);

        /*
         * test3333 の値を含む物の数を取得
         */
        var a = msgList.stream()
            .flatMap(msg -> msg.entrySet().stream())
            .filter(entry -> entry.getValue().contains("test3333"))
            .count();

        // a : 1
        System.out.println("a: " + a);

        /*
         * test3333 の値を含む物を取得
         */
        var b = msgList.stream()
            .flatMap(msg -> msg.entrySet().stream())
            .filter(entry -> entry.getValue().contains("test3333"))
            .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));

        // b: {1=test3333[warning_727]}
        System.out.println("b: " + b);

        /*
         * warning_726 の値が含まれない物を全て取得
         */
        msgList = msgList.stream()
            .filter(map -> map.entrySet().stream()
                .noneMatch(entry -> entry.getValue().contains("warning_726")))
            .collect(Collectors.toList());

        /*
         * warning_727 の値が含まれない物を全て取得
         */
        msgList = msgList.stream()
            .filter(map -> map.entrySet().stream()
                .noneMatch(entry -> entry.getValue().contains("warning_727")))
            .collect(Collectors.toList());

        // msgList: [{1=test2[warning_736]}, {1=test21[914_warning]}, {1=test255[warning_737]}, {2=error_728}]
        System.out.println("msgList: " + msgList);
    }
}