import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
 
public class P017 {
  public static void main(String[] args) {
    IntList il1 = new IntList(3);
    System.out.println(il1);
 
    IntList il2 = il1.reverse();
    System.out.println(il2);
 
    IntList il3 = il1.concat(il2);
    System.out.println(il3);
    System.out.println(il3.sum());
 
    // 【重要】元のデータが破壊されてないか、必ずチェックすること
    System.out.println(il1);
    System.out.println(il2);
  }
}
 
class IntList {
  List<Integer> list = new ArrayList<Integer>();// フィールド
 
  // ② 引数無しのコンストラクタ：list を空のリストで初期化する．
  IntList() {
  }
 
  // ③ int 型の引数 n をとるコンストラクタ：list を 1～n の n 個の整数を要素とするリスト にする．
  IntList(int n) { // コンストラクタ
    for (int i = 1; i <= n; i++) {
      list.add(i);
    }
  }
 
  void add(int n) {
    list.add(n);
  }
 
  int get(int i) {
    return list.get(i);
  }
 
  int size() {
    return list.size();
  }
 
  // ⑦ IntList reverse()：この整数リストの内容を反転した整数リストを作成
  IntList reverse() {
    IntList il2 = concat(null);
    try {
      Collections.reverse(il2.list);
    } catch (UnsupportedOperationException ex) {
      ex.printStackTrace();
    }
    return il2;
  }
 
  // ⑧ IntList concat(IntList l)：この整数リストの末尾に別の整数リスト l の内容を追加し たリストを作成し，IntList オブ
  // ジェクトとして返す
  IntList concat(IntList l) {
    IntList il2 = new IntList();
    // クローン(Shallow Copy)、Deep Copyでは無い
    il2.list = new ArrayList<Integer>(list);
    if (l != null) {
      il2.list.addAll(l.list);
    }
    return il2;
  }
 
  // ⑨ int sum()：この整数リストに含まれる整数の総和を返す．
  int sum() {
    int a = 0;
    for (Integer i : list) {
      a += i;
    }
    return a;
  }
 
  // print文で使えるようにしている
  @Override
  public String toString() {
    return list.toString();
  }
}
 

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