Collections_Framework

import java.util.Collections;;
import java.util.Map;
import java.util.List;
import java.util.Arrays;
import java.util.stream.Collectors;
// Collections_Framework

class /*Main*/Collections_Framework {
  //
  public static void main(String[] args) {
    //
    Map<String, Integer> s_M = Collections.singletonMap("key_1", 1);
    //
    System.out.println("hello world");
    System.out.println(s_M);
    s_M.forEach((k, v) -> {
        System.out.println("k:" + k);
        System.out.println("v:" + v);
      }
    );
    System.out.println(s_M.entrySet());
    System.out.println(s_M.entrySet().toArray()[0]);
    //
    List<Character> l_C = Collections.nCopies(9, '#');
    //
    System.out.println(l_C);
    // fromIndex, inclusive, and toIndex, exclusive
    List<Character> sub_L_3 = l_C.subList(0, 3);
    //
    System.out.println(sub_L_3);
    //CharSequence
    char[] chars = new char[9];
    System.out.println(
      sub_L_3
        .stream()
        .map(i -> i.toString())
        .collect(Collectors.joining(""))
    );
    System.out.println(sub_L_3.listIterator(0).next());
    /// ### .mkString analog ### ///
    List<Integer> numbers = Arrays.asList(1, 2, 3, 4);
    String commaSeparatedNumbers = numbers
      .stream()
      .map(i -> i.toString())
      .collect(Collectors.joining(", "));
    //
    System.out.println(commaSeparatedNumbers);
    //
  }
  //
}