EnumSample.java

package jp.co.confrage;

import java.util.Arrays;
import java.util.stream.Collectors;

public class EnumSample {
  public static void main(String[] args) {
    var ret =
        Arrays.stream(Week.values())
            .map(
                e -> {
                  return e.name();
                })
            .collect(Collectors.toMap(k -> k, v -> v));

    System.out.println(ret); // {Monday=Monday, Tursday=Tursday, Friday=Friday, Sunday=Sunday, Wednesday=Wednesday, Tuesday=Tuesday, Saturday=Saturday}
  }
}