[{"_1":2,"_578":-5,"_579":-5},"loaderData",{"_3":4},"routes/present",{"_5":6,"_7":8},"deckKey","luagate/java-intro-practice","slides",[9,23,34,41,74,99,106,116,124,134,139,144,154,159,168,178,183,192,197,207,212,218,227,232,241,246,255,264,269,278,283,292,297,303,312,317,326,331,337,346,351,360,369,378,387,392,402,407,416,421,427,436,441,450,455,466,472,481,521,531,536,545,550,563,570],{"_10":11,"_12":13,"_14":15,"_13":16,"_17":18,"_19":20,"_21":22},"id",1,"type","title","cover",true,"Javaプログラミング演習編","subtitle","手を動かして学ぶ全25問","category","Java演習","theme","light",{"_10":24,"_12":25,"_13":26,"_19":20,"_27":28,"_29":30,"_21":22},2,"toc","目次（前半）","heading","演習の流れ","items",[31,32,33],"1. 入門編の演習（変数・分岐・繰り返し）","2. 制御構造の演習（for・switch・ネスト）","3. 配列の演習（1次元・2次元）",{"_10":35,"_12":25,"_13":36,"_19":20,"_27":28,"_29":37,"_21":22},3,"目次（後半）",[38,39,40],"4. メソッドの演習（引数・戻り値・オーバーロード）","5. データ型変換の演習","6. デバッグと例外処理の演習",{"_10":42,"_12":43,"_13":44,"_19":20,"_45":46,"_43":47,"_21":22},4,"cards","演習の進め方","description","効果的に演習を進める4つのポイント。",[48,56,62,68],{"_27":49,"_50":51,"_52":53},"まず手を動かす","icon","edit-3","bullets",[54,55],"完璧でなくてOK","エラーから学ぶ",{"_27":57,"_50":58,"_52":59},"フローを描く","git-branch",[60,61],"コーディング前に流れを整理","複雑な分岐ほど効果的",{"_27":63,"_50":64,"_52":65},"トレースする","search",[66,67],"値の変化を追う","F6 ステップ実行を活用",{"_27":69,"_50":70,"_52":71},"質問する","help-circle",[72,73],"詰まったら早めに相談","他の人と解法を比べる",{"_10":75,"_12":76,"_13":77,"_19":20,"_45":78,"_79":80,"_97":98,"_21":22},5,"bar-chart","演習問題の章別配分","全25問を章ごとに分類した内訳です。","data",[81,86,89,91,93,95],{"_82":83,"_84":85},"label","入門編","value",8,{"_82":87,"_84":88},"制御構造",6,{"_82":90,"_84":24},"配列",{"_82":92,"_84":88},"メソッド",{"_82":94,"_84":24},"型変換",{"_82":96,"_84":11},"その他","unit","問",{"_10":100,"_12":13,"_13":101,"_17":102,"_103":104,"_19":105,"_21":22},10,"入門編の演習","変数・計算・分岐・繰り返し","section","1","Java演習 - 入門編",{"_10":107,"_12":108,"_13":109,"_19":105,"_45":110,"_52":111},11,"content","P1-01 数値型の初期化と計算","数値型の宣言・初期化・計算を行う2つのプログラムを作成しよう。",[112,113,114,115],"Keisan1.java：int型 tate=10, yoko=5, menseki に長方形の面積を代入し表示","Keisan2.java：double型 hankei=8.0 で hankei × hankei × 3.14 を表示","表示は System.out.println(〇〇) を使う","〇〇には変数や計算式を直接書ける",{"_10":117,"_12":118,"_13":119,"_19":105,"_45":120,"_118":121,"_122":123,"_21":22},12,"code","P1-01 解答例（Keisan1.java）","長方形の面積を計算して表示します。","public class Keisan1 {\n public static void main(String[] args) {\n int tate = 10;\n int yoko = 5;\n int menseki;\n menseki = tate * yoko / 2;\n System.out.println(menseki); // 25\n }\n}","language","java",{"_10":125,"_12":108,"_13":126,"_19":105,"_45":127,"_52":128},13,"P1-02 文字列の扱い","文字列型と数値型を組み合わせるプログラムを作成しよう。",[129,130,131,132,133],"Moji1.java：String name を任意の名前で初期化し、挨拶と一緒に表示","出力例：「こんにちは、山田さん。」","Moji2.java：int gekkyu と int zangyo を初期化","「あなたの月額給与は〇〇」を1行で表示。〇〇は gekkyu + zangyo","上級編：変数は gekkyu と zangyo の2つだけで実装",{"_10":135,"_12":118,"_13":136,"_19":105,"_45":137,"_118":138,"_122":123,"_21":22},14,"P1-02 解答例（Moji2.java 上級）","変数を2つだけ使って合計給与を表示します。","public class Moji2 {\n public static void main(String[] args) {\n int gekkyu = 200000;\n int zangyo = 15000;\n // 合計用の新しい変数を使わずに、計算式を直接埋め込む\n System.out.println(\"あなたの月額給与は \" + (gekkyu + zangyo));\n }\n}",{"_10":140,"_12":118,"_13":141,"_19":105,"_45":142,"_118":143,"_122":123,"_21":22},15,"P1-03 条件式の書き方","出力メッセージに合致するように、条件式の(1)(2)を完成させよう。","// (1) 比較演算子（不等号）\nif ( /* (1) */ ) {\n System.out.println(\"合計額は10000以下です\");\n} else {\n System.out.println(\"合計額は10000より大きくなりました\");\n}\n\n// (2) 比較演算子（等号）\nif ( /* (2) */ ) {\n System.out.println(\"合計額は10000ではありません\");\n} else {\n System.out.println(\"合計額は10000です\");\n}\n\n// 解答: (1) total <= 10000 (2) total != 10000",{"_10":145,"_12":108,"_13":146,"_19":105,"_45":147,"_52":148},16,"P1-04 分岐を作ってみよう（1）","年齢による入場料判定プログラムを作成しよう（クラス名: Bunki1）。",[149,150,151,152,153],"int age を任意の値で初期化","age < 20 が true なら「入場料は未成年割引で1000円です。」","false なら「入場料は1500円です。」","ageが22のとき → 「入場料は1500円です。」","条件分岐の両方を通るパターンで動作確認",{"_10":155,"_12":118,"_13":156,"_19":105,"_45":157,"_118":158,"_122":123,"_21":22},17,"P1-04 解答例（Bunki1.java）","if-else でシンプルに分岐する例。","public class Bunki1 {\n public static void main(String[] args) {\n int age = 22;\n if (age < 20) {\n System.out.println(\"入場料は未成年割引で1000円です。\");\n } else {\n System.out.println(\"入場料は1500円です。\");\n }\n }\n}",{"_10":160,"_12":108,"_13":161,"_19":105,"_45":162,"_52":163},18,"P1-04 分岐を作ってみよう（2）","P1-04(1)を、文字列の連結で組み立てるバージョン（Bunki2）。",[164,165,166,167],"int age, int charge=1500, String comment=\"入場料は\" を初期化","age < 20 のとき: comment に「未成年割引で」を追記、charge を 1000 に","最後に comment + charge + \"円です。\" を表示","出力例（age=19）: 入場料は未成年割引で1000円です。",{"_10":169,"_12":108,"_13":170,"_19":105,"_45":171,"_52":172},19,"P1-05 料金判定プログラム","年齢入力から料金区分を判定するプログラム（クラス名: JudgeFee）。",[173,174,175,176,177],"ユーザーは年齢を整数で入力","60以上 → 「シルバー割引を適用します。」 + 1500円","13未満 → 「子供料金を適用します。」 + 1000円","それ以外 → 3000円","最後に「入場料金は〇〇円です。」を表示",{"_10":179,"_12":118,"_13":180,"_19":105,"_45":181,"_118":182,"_122":123,"_21":22},20,"P1-05 解答例（JudgeFee.java）","年齢で料金区分を判定する例。","import java.util.Scanner;\n\npublic class JudgeFee {\n public static void main(String[] args) {\n Scanner scan = new Scanner(System.in);\n System.out.print(\"あなたの年齢を入力してください: \");\n int age = scan.nextInt();\n int fee;\n if (age >= 60) {\n System.out.println(\"シルバー割引を適用します。\");\n fee = 1500;\n } else if (age < 13) {\n System.out.println(\"子供料金を適用します。\");\n fee = 1000;\n } else {\n fee = 3000;\n }\n System.out.println(\"入場料金は \" + fee + \" 円です。\");\n }\n}",{"_10":184,"_12":108,"_13":185,"_19":105,"_45":186,"_52":187},21,"P1-06 奇偶判定プログラム","入力された整数の奇偶を判定するプログラム（クラス名: Kigu）。",[188,189,190,191],"ユーザーは整数を入力","2で割った余りが0 → 「偶数」","余りが0でない → 「奇数」","ヒント: 剰余演算子 % を使う",{"_10":193,"_12":118,"_13":194,"_19":105,"_45":195,"_118":196,"_122":123,"_21":22},22,"P1-07 1〜100の合計","穴埋めを完成させて、1から100までの合計を出力するプログラムを作ろう。","public class Add1to100 {\n public static void main(String[] args) {\n int num = 0;\n int ans = 0;\n while ( /* ? */ ) { // 解答: num < 100\n num = num + 1;\n ans = ans + num;\n }\n System.out.println(\"答えは:\" + ans); // 答えは:5050\n }\n}",{"_10":198,"_12":108,"_13":199,"_19":105,"_45":200,"_52":201},23,"P1-08 Just100! ゲーム","複数の整数を入力し合計が100になるか超えるまで繰り返す（クラス名: Just100）。",[202,203,204,205,206],"sum を 0 で初期化","while ループで「数字を入力してください:」を表示し整数を入力","入力値を sum に加算","sum == 100 → 「Just 100!」を表示して終了","sum > 100 → 「Over!」を表示して終了",{"_10":208,"_12":118,"_13":209,"_19":105,"_45":210,"_118":211,"_122":123,"_21":22},24,"P1-08 解答例（Just100.java）","無限ループ + break で「ちょうど」「超えた」の判定を行う例。","import java.util.Scanner;\n\npublic class Just100 {\n public static void main(String[] args) {\n Scanner scan = new Scanner(System.in);\n int sum = 0;\n while (true) {\n System.out.print(\"数字を入力してください: \");\n int input = scan.nextInt();\n sum += input;\n if (sum == 100) {\n System.out.println(\"Just 100!\");\n break;\n }\n if (sum > 100) {\n System.out.println(\"Over!\");\n break;\n }\n }\n }\n}",{"_10":213,"_12":13,"_13":214,"_17":215,"_103":216,"_19":217,"_21":22},30,"制御構造の演習","for・switch・ネスト・break","2","Java演習 - 制御構造",{"_10":219,"_12":108,"_13":220,"_19":217,"_45":221,"_52":222},31,"P2-01 定数を使ってみよう","既存の TryGradExam クラスのハードコーディング箇所を定数に置き換えよう。",[223,224,225,226],"英語と数学の点数入力を受け、合計100点以上で進級","ハードコーディングされている100、上限点、下限点を final 定数に","定数名は意味が伝わるように工夫（例: PASSING_SCORE, MAX_SCORE）","定数を使うことで意図が読み取りやすくなる",{"_10":228,"_12":118,"_13":229,"_19":217,"_45":230,"_118":231,"_122":123,"_21":22},32,"P2-01 改善前後の比較","ハードコーディングを定数に変えるイメージ。","// 改善前\nif (english > 100) { System.out.println(\"範囲外\"); return; }\nif (english < 0) { System.out.println(\"範囲外\"); return; }\n\n// 改善後\nfinal int MAX_SCORE = 100;\nfinal int MIN_SCORE = 0;\nfinal int PASSING_TOTAL = 100;\nif (english > MAX_SCORE) { System.out.println(\"範囲外\"); return; }\nif (english < MIN_SCORE) { System.out.println(\"範囲外\"); return; }",{"_10":233,"_12":108,"_13":234,"_19":217,"_45":235,"_52":236},33,"P2-02 反復処理を記述しよう","3つの反復処理パターンをfor文で実装しよう。",[237,238,239,240],"AddNumber: 入力した n について 1〜n の整数の合計を表示","AddOddNumber: 1〜n の奇数だけの合計を表示（i % 2 != 0 で判定）","AddInputNumber: 最初に n を入力、次に n 回数値を入力、合計を表示","出力例: 「合計は: 32」",{"_10":242,"_12":118,"_13":243,"_19":217,"_45":244,"_118":245,"_122":123,"_21":22},34,"P2-02 解答例（AddOddNumber.java）","奇数だけを合計する典型例。","import java.util.Scanner;\n\npublic class AddOddNumber {\n public static void main(String[] args) {\n Scanner scan = new Scanner(System.in);\n System.out.print(\"n を入力: \");\n int n = scan.nextInt();\n int sum = 0;\n for (int i = 1; i <= n; i++) {\n if (i % 2 != 0) { // 奇数のみ\n sum += i;\n }\n }\n System.out.println(\"合計: \" + sum);\n }\n}",{"_10":247,"_12":108,"_13":248,"_19":217,"_45":249,"_52":250},35,"P2-03 制御構造のネスト","奇偶判定を10回繰り返し、それぞれの個数を表示するプログラム（クラス名: CountOddEven）。",[251,252,253,254],"数値を10回入力させる（for ループで10回）","各値の奇偶を if で判定し、それぞれカウント","ループ終了後、奇数と偶数の個数を表示","出力例: 「偶数は 4 回 / 奇数は 6 回入力されました」",{"_10":256,"_12":108,"_13":257,"_19":217,"_45":258,"_52":259},36,"P2-04 二重ループ構造（九九）","九九の表を出力するプログラムを2つ作成しよう。",[260,261,262,263],"Kuku.java: 9行9列で九九を出力","Kuku2.java: 整列した見やすい版（桁揃え）","ヒント: System.out.print と System.out.println を使い分け","print は改行なし、println は改行あり",{"_10":265,"_12":118,"_13":266,"_19":217,"_45":267,"_118":268,"_122":123,"_21":22},37,"P2-04 解答例（Kuku2.java）","二重ループ + 桁揃えで整った九九表を出力。","public class Kuku2 {\n public static void main(String[] args) {\n for (int x = 1; x <= 9; x++) {\n for (int y = 1; y <= 9; y++) {\n // %3d で右寄せ3桁\n System.out.printf(\"%3d\", x * y);\n }\n System.out.println(); // 行末で改行\n }\n }\n}",{"_10":270,"_12":108,"_13":271,"_19":217,"_45":272,"_52":273},38,"P2-05 多肢選択を書いてみよう","switch文と if-else の使い分け演習を2つ。",[274,275,276,277],"JudgePass: 英語・国語・数学の点数を入力、1科目でも70未満で「不合格」","GetWeekdayName: 曜日番号(1-7)を入力、日本語の曜日名を出力","ISO 8601: 月=1, 火=2, 水=3, 木=4, 金=5, 土=6, 日=7","不正な入力には「入力エラー」を表示",{"_10":279,"_12":118,"_13":280,"_19":217,"_45":281,"_118":282,"_122":123,"_21":22},39,"P2-05 解答例（GetWeekdayName.java）","switch文で曜日番号を曜日名に変換する例。","import java.util.Scanner;\n\npublic class GetWeekdayName {\n public static void main(String[] args) {\n Scanner scan = new Scanner(System.in);\n System.out.print(\"曜日番号を入力してください: \");\n int num = scan.nextInt();\n switch (num) {\n case 1: System.out.println(\"それは月曜日です。\"); break;\n case 2: System.out.println(\"それは火曜日です。\"); break;\n case 3: System.out.println(\"それは水曜日です。\"); break;\n case 4: System.out.println(\"それは木曜日です。\"); break;\n case 5: System.out.println(\"それは金曜日です。\"); break;\n case 6: System.out.println(\"それは土曜日です。\"); break;\n case 7: System.out.println(\"それは日曜日です。\"); break;\n default: System.out.println(\"入力エラー\");\n }\n }\n}",{"_10":284,"_12":108,"_13":285,"_19":217,"_45":286,"_52":287},40,"P2-06 複合条件（うるう年判定）","うるう年の3条件を複合条件式で実装（クラス名: JudgeLeapYear）。",[288,289,290,291],"条件①: 西暦年が4で割り切れる年はうるう年","条件②: 西暦年が100で割り切れる年はうるう年ではない","条件③: 西暦年が400で割り切れる年はうるう年","正しい論理式: (year%4==0 && year%100!=0) || year%400==0",{"_10":293,"_12":118,"_13":294,"_19":217,"_45":295,"_118":296,"_122":123,"_21":22},41,"P2-06 解答例（JudgeLeapYear.java）","うるう年判定の論理式を1つの if にまとめる。","import java.util.Scanner;\n\npublic class JudgeLeapYear {\n public static void main(String[] args) {\n Scanner scan = new Scanner(System.in);\n System.out.print(\"西暦を入力: \");\n int year = scan.nextInt();\n if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) {\n System.out.println(\"うるう年\");\n } else {\n System.out.println(\"うるう年ではない\");\n }\n }\n}",{"_10":298,"_12":13,"_13":299,"_17":300,"_103":301,"_19":302,"_21":22},50,"配列の演習","1次元配列・2次元配列","3","Java演習 - 配列",{"_10":304,"_12":108,"_13":305,"_19":302,"_45":306,"_52":307},51,"P2-07 配列の操作練習","1次元配列の基本操作を2問。",[308,309,310,311],"ArraySum: 整数配列（要素2個以上）を定義、全要素の合計値を表示","ArrayReverse: 10個の文字列を入力し配列に格納、逆順で表示","scan.next() で文字列を入力する（nextInt() ではない）","ループを2つ使う：入力用と出力用",{"_10":313,"_12":118,"_13":314,"_19":302,"_45":315,"_118":316,"_122":123,"_21":22},52,"P2-07 解答例（ArrayReverse.java）","配列に格納した文字列を逆順で表示する例。","import java.util.Scanner;\n\npublic class ArrayReverse {\n public static void main(String[] args) {\n Scanner scan = new Scanner(System.in);\n String[] array = new String[10];\n\n // 入力ループ\n for (int i = 0; i < array.length; i++) {\n System.out.print(\"入力 \" + (i + 1) + \": \");\n array[i] = scan.next();\n }\n\n // 逆順表示ループ\n for (int i = array.length - 1; i >= 0; i--) {\n System.out.println(array[i]);\n }\n }\n}",{"_10":318,"_12":108,"_13":319,"_19":302,"_45":320,"_52":321},53,"P2-08 2次元配列の操作練習","九九の値を2次元配列に格納するプログラム（クラス名: KukuArray）。",[322,323,324,325],"int[][] kuku = new int[9][9]; で2次元配列を確保","二重 for ループで kuku[i][j] = (i+1) * (j+1) を代入","格納するだけでは画面に何も表示されない","検証用に表示コードを別途書いてみる",{"_10":327,"_12":118,"_13":328,"_19":302,"_45":329,"_118":330,"_122":123,"_21":22},54,"P2-08 解答例（KukuArray.java）","2次元配列への代入と検証用表示を組み合わせた例。","public class KukuArray {\n public static void main(String[] args) {\n int[][] kuku = new int[9][9];\n // 値の代入\n for (int i = 0; i < 9; i++) {\n for (int j = 0; j < 9; j++) {\n kuku[i][j] = (i + 1) * (j + 1);\n }\n }\n // 検証用表示\n for (int i = 0; i < 9; i++) {\n for (int j = 0; j < 9; j++) {\n System.out.printf(\"%3d\", kuku[i][j]);\n }\n System.out.println();\n }\n }\n}",{"_10":332,"_12":13,"_13":333,"_17":334,"_103":335,"_19":336,"_21":22},70,"メソッドの演習","引数・戻り値・オーバーロード","4","Java演習 - メソッド",{"_10":338,"_12":108,"_13":339,"_19":336,"_45":340,"_52":341},71,"P3-01 引数と戻り値の練習","4つのメソッドを実装してみよう。",[342,343,344,345],"hello: 引数なし、戻り値なし。「Hello!」を出力","greet: String を受けて、その文字列を出力","luckyNumber: 引数なし、1〜10のランダム整数を返す","calcSquare: int を受けて、その2乗を返す",{"_10":347,"_12":118,"_13":348,"_19":336,"_45":349,"_118":350,"_122":123,"_21":22},72,"P3-01 解答例","4つのメソッドのシグネチャと処理。","public class TryMethods {\n public static void main(String[] args) {\n hello();\n greet(\"こんにちは\");\n System.out.println(\"ラッキーナンバーは \" + luckyNumber());\n System.out.println(\"一辺 3 の正方形の面積は \" + calcSquare(3));\n }\n\n static void hello() {\n System.out.println(\"Hello!\");\n }\n static void greet(String msg) {\n System.out.println(msg);\n }\n static int luckyNumber() {\n return (int)(Math.random() * 10) + 1; // 1〜10\n }\n static int calcSquare(int n) {\n return n * n;\n }\n}",{"_10":352,"_12":108,"_13":353,"_19":336,"_45":354,"_52":355},73,"P3-02 メソッドの仕様変更","回転寿司の会計計算を仕様変更しよう。",[356,357,358,359],"①: 同じ色の皿を4皿以上注文すると1皿無料（CalcSushiPayment2）","②: ①に追加。300円以上の皿には1皿無料を適用しない（CalcSushiPayment3）","ヒント: 皿数 - 1 を計算する条件分岐を追加","出力例: 「お会計金額は 1450 円です」",{"_10":361,"_12":108,"_13":362,"_19":336,"_45":363,"_52":364},74,"P3-03 メソッドの理解の確認","既存のソースコードを読み解く演習。",[365,366,367,368],"S3-01 のコードのウォークスルーを行う","プログラム実行から終了までの処理順序を説明できるようになる","変数の値の変化を順番に追う（トレース）","他の人に説明することで理解が深まる",{"_10":370,"_12":108,"_13":371,"_19":336,"_45":372,"_52":373},75,"P3-03 メソッドを使ってみよう（最大公約数）","既存メソッドを呼び出して結果を表示するプログラム（クラス名: ShowGcd）。",[374,375,376,377],"ShowGcd には calcGcd メソッドが既に実装されている","2つの数値を入力し calcGcd を呼び出して最大公約数を表示","入力例: 912 と 642 → 結果: 6","calcGcd の中身は理解しなくてOK。使い方の練習",{"_10":379,"_12":108,"_13":380,"_19":336,"_45":381,"_52":382},76,"P3-04 メソッドを作ってみよう（台形）","台形の面積を計算するメソッドを実装（クラス名: ShowTrapezoidArea）。",[383,384,385,386],"ユーザーは上底・下底・高さを double で入力","calcTrapezoidArea(double, double, double) を新規実装","台形の面積 = (上底 + 下底) × 高さ ÷ 2","double を入力するには scan.nextDouble() を使う",{"_10":388,"_12":118,"_13":389,"_19":336,"_45":390,"_118":391,"_122":123,"_21":22},77,"P3-04 解答例（ShowTrapezoidArea.java）","台形面積メソッドのシグネチャと呼び出し例。","import java.util.Scanner;\n\npublic class ShowTrapezoidArea {\n public static void main(String[] args) {\n Scanner scan = new Scanner(System.in);\n System.out.print(\"上底を入力: \"); double top = scan.nextDouble();\n System.out.print(\"下底を入力: \"); double bottom = scan.nextDouble();\n System.out.print(\"高さを入力: \"); double height = scan.nextDouble();\n double area = calcTrapezoidArea(top, bottom, height);\n System.out.println(\"面積は: \" + area);\n }\n\n static double calcTrapezoidArea(double top, double bottom, double height) {\n return (top + bottom) * height / 2;\n }\n}",{"_10":393,"_12":108,"_13":394,"_19":336,"_45":395,"_52":396},78,"P3-05 プログラムの引数のチェック","main の引数（コマンドライン引数）の数をチェックするコードに改修しよう。",[397,398,399,400,401],"プログラムは「名前」「年齢」「職業」の3つを引数として受け取る","引数が3つ未満 → エラー終了","引数が4つ以上 → 4つ目以降は無視（同様にエラー終了で良い）","エラー時のメッセージ: 「引数は３つ（名前、年齢、職業）です。」","ヒント: args.length で個数取得、return; で main を終了",{"_10":403,"_12":118,"_13":404,"_19":336,"_45":405,"_118":406,"_122":123,"_21":22},79,"P3-05 解答例","引数チェックの典型パターン。","public class MainArgsCheck {\n public static void main(String[] args) {\n if (args.length != 3) {\n System.out.println(\"引数は３つ（名前、年齢、職業）です。\");\n return;\n }\n String name = args[0];\n int age = Integer.parseInt(args[1]);\n String job = args[2];\n System.out.println(\"Hello! \" + name + \".\");\n System.out.println(\"You are \" + age + \" years old \" + job + \"...\");\n }\n}",{"_10":408,"_12":108,"_13":409,"_19":336,"_45":410,"_52":411},80,"P3-06 オーバーロードの実装","calcArea メソッドのオーバーロードを2つ追加しよう。",[412,413,414,415],"既存: calcArea(int width, int height) → 長方形","追加①: calcArea(int side) → 正方形","追加②: calcArea(int top, int bottom, int height) → 台形","期待出力: 「幅 10 高さ 8 の長方形の面積は 80」「一辺 9 の正方形の面積は 81」「上底 7 下底 10 高さ 5 の台形の面積は 42」",{"_10":417,"_12":118,"_13":418,"_19":336,"_45":419,"_118":420,"_122":123,"_21":22},81,"P3-06 解答例（PrcOverload.java）","オーバーロードで同名メソッドを複数定義する例。","public class PrcOverload {\n public static void main(String[] args) {\n calcArea(10, 8);\n calcArea(9);\n calcArea(7, 10, 5);\n }\n\n static void calcArea(int width, int height) {\n System.out.println(\"幅 \" + width + \" 高さ \" + height + \" の長方形の面積は \" + (width * height));\n }\n static void calcArea(int side) {\n System.out.println(\"一辺 \" + side + \" の正方形の面積は \" + (side * side));\n }\n static void calcArea(int top, int bottom, int height) {\n int area = (top + bottom) * height / 2;\n System.out.println(\"上底 \" + top + \" 下底 \" + bottom + \" 高さ \" + height + \" の台形の面積は \" + area);\n }\n}",{"_10":422,"_12":13,"_13":423,"_17":424,"_103":425,"_19":426,"_21":22},90,"データ型変換の演習","自動型変換・キャスト・parseInt","5","Java演習 - 型変換",{"_10":428,"_12":108,"_13":429,"_19":426,"_45":430,"_52":431},91,"P3-07 式と値","既存メソッド（add, sub, mul）を組み合わせて、四則演算と同じ優先順位で計算しよう。",[432,433,434,435],"割り算メソッドは用意されていない（Javaの / 演算子を使う）","各穴埋めは1行で記述する","計算の途中で値を保持する変数は使わない","期待出力: 1+2=3, 1+2-3=0, 1×2+3=5, 1+2×3=7, 4×3-5÷2=10",{"_10":437,"_12":118,"_13":438,"_19":426,"_45":439,"_118":440,"_122":123,"_21":22},92,"P3-07 解答イメージ","add/sub/mul を入れ子にして優先順位を表現。","// (1) 1+2 = 3\nadd(1, 2)\n\n// (2) 1+2-3 = 0\nsub(add(1, 2), 3)\n\n// (3) 1×2+3 = 5\nadd(mul(1, 2), 3)\n\n// (4) 1+2×3 = 7\nadd(1, mul(2, 3))\n\n// (5) 4×3-5÷2 = 10\nsub(mul(4, 3), 5/2) // 5/2 はint割り算なので 2",{"_10":442,"_12":108,"_13":443,"_19":426,"_45":444,"_52":445},93,"P3-08 型変換を練習しよう","既存プログラムの型変換に関する2つの問題を修正しよう。",[446,447,448,449],"課題①: テストの平均点を整数ではなく小数まで含めて表示","課題②: 所得税総額の計算結果が正しくない（int の範囲を超えている）","①ヒント: scoreSum / scores.length を double にキャスト","②ヒント: workers と incomeTaxPerWorker のどちらかを long 型に変更",{"_10":451,"_12":118,"_13":452,"_19":426,"_45":453,"_118":454,"_122":123,"_21":22},94,"P3-08 解答例","int の桁あふれと小数表示の対応。","// 課題①: 平均点を小数で\ndouble avg = (double) scoreSum / scores.length;\nSystem.out.println(\"平均点は、\" + avg); // 71.5\n\n// 課題②: long で計算する\nlong workers = 50000000L; // 末尾Lでlongリテラル\nlong incomeTaxPerWorker = 170000L;\nSystem.out.println(\"所得税の総額は、\" + (workers * incomeTaxPerWorker));\n// 8500000000000",{"_10":456,"_12":108,"_13":457,"_19":426,"_45":458,"_52":459},95,"P3-09 整数型への型変換","プログラム引数を整数に変換するプログラム（クラス名: DayCountFor30）。",[460,461,462,463,464,465],"引数は2個（名前、年齢）","引数の数が2でなければエラー終了","args[1] を Integer.parseInt で int に変換","age < 30 なら「nameさんの30歳までの日数は多くても dayRemain日です。」","それ以外は「nameさんは既に30歳です」","dayRemain = (30 - age) × 365",{"_10":467,"_12":13,"_13":468,"_17":469,"_103":470,"_19":471,"_21":22},110,"デバッグと例外処理の演習","トレースとエラー対応","6","Java演習 - デバッグ",{"_10":473,"_12":108,"_13":474,"_19":471,"_45":475,"_52":476},111,"プログラムのトレース演習","Eclipse のデバッグ機能でプログラムの動きを追跡しよう。",[477,478,479,480],"ShowGcd クラスを動作させ、calcGcd メソッド内でステップ実行","入力: 320 と 115 で実行","ループ回数ごとに a, b, rem の値を記録（トレース表）","変数ビューで値の変化を観察",{"_10":482,"_12":483,"_13":484,"_19":471,"_45":485,"_486":487,"_492":493,"_496":497},112,"table","トレース表のサンプル","calcGcd メソッドのループでの値変化（入力: 320, 115）。","headers",[488,489,490,491],"ループ回数","aの値","bの値","remの値","headerIcons",[494,495,495,495],"repeat","tag","rows",[498,503,506,509,512,515,517],[499,500,501,502],"開始","320","115","-",[504,501,505,505],"1回目","90",[507,505,508,508],"2回目","25",[510,508,511,511],"3回目","15",[513,511,514,514],"4回目","10",[516,514,425,425],"5回目",[518,425,519,520],"6回目","0","0（終了）",{"_10":522,"_12":108,"_13":523,"_19":524,"_45":525,"_52":526},113,"例外処理のトレース演習","Java演習 - 例外処理","TryExceptionHandling クラスで例外発生時の挙動を確認しよう。",[527,528,529,530],"正常系（10/2など）で実行 → catchブロックは実行されない","0除算で実行 → catchブロックに入る、Exception e に詳細が格納","数値以外（\"abc\"）を入力 → 別の例外（InputMismatchException）","変数ビューで Exception e の中身を確認",{"_10":532,"_12":118,"_13":533,"_19":524,"_45":534,"_118":535,"_122":123,"_21":22},114,"例外発生パターンの観察","3つの入力パターンで例外がどう変わるか確認する。","try {\n Scanner scan = new Scanner(System.in);\n System.out.print(\"分子: \");\n int a = scan.nextInt();\n System.out.print(\"分母: \");\n int b = scan.nextInt();\n int result = a / b;\n System.out.println(\"結果: \" + result);\n}\ncatch (Exception e) {\n // ここにブレークポイントを置いて e の中身を見る\n System.out.println(\"例外: \" + e.getClass().getSimpleName());\n System.out.println(\"メッセージ: \" + e.getMessage());\n}\n\n// 入力パターン:\n// 1) 10, 2 → 例外なし\n// 2) 10, 0 → ArithmeticException: / by zero\n// 3) 10, abc → InputMismatchException",{"_10":537,"_12":108,"_13":538,"_19":524,"_45":539,"_52":540},115,"参考編 P4-01 文字型を扱ってみよう","char型を使った文字列操作の演習（参考編）。",[541,542,543,544],"WidePrint: \"HELLO!\" を1文字おきにスペース挟んで表示 → 「H E L L O !」","WidePrint2: 上記をユーザー入力した文字列で実現","ヒント: str.length() で文字列の長さ、str.charAt(i) で1文字取得","ReverseString: \"NOW I WON !\" を char配列に格納し、逆順表示",{"_10":546,"_12":118,"_13":547,"_19":524,"_45":548,"_118":549,"_122":123,"_21":22},116,"P4-01 解答例（WidePrint.java）","charAt を使って1文字ずつ取り出して間にスペースを挟む例。","public class WidePrint {\n public static void main(String[] args) {\n String s = \"HELLO!\";\n for (int i = 0; i < s.length(); i++) {\n System.out.print(s.charAt(i));\n if (i < s.length() - 1) {\n System.out.print(\" \");\n }\n }\n System.out.println(); // H E L L O !\n }\n}",{"_10":551,"_12":552,"_13":553,"_19":20,"_45":554,"_555":556,"_557":558},120,"quiz","演習総まとめクイズ","演習全体の理解を確認しましょう。","question","P3-08（所得税の総額）で、int * int の結果が桁あふれするのを防ぐ正しい対処はどれ？","choices",[559,560,561,562],"int を short に変える","片方を long 型にする（例: long workers = ...）","両方を String にする","System.out.println を使わない",{"_10":564,"_12":565,"_13":566,"_19":20,"_45":567,"_555":556,"_557":568,"_569":11},121,"quiz-answer","演習総まとめクイズ解答","int 同士の掛け算は int の範囲（約±21億）に収まる必要があります。それを超える可能性がある場合、片方を long にすることで自動型変換が働き、計算結果も long 型になります。",[559,560,561,562],"correctIndex",{"_10":571,"_12":572,"_13":573,"_19":20,"_21":574,"_572":575,"_576":577},130,"quote","演習おつかれさまでした","accent","手を動かして書いたコードは、読んで覚えたコードの10倍身につく。詰まった所こそ最大の学習ポイント。","source","Javaプログラミング演習編完結","actionData","errors"]

Javaプログラミング 演習編

Javaプログラミング演習編