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筋トレ大好きな文系女学生のJava入門〜式と演算子〜 ref: http://qiita.com/amippy/items/28130139a60e66ebb7a7
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【代表的な算術演算子】 | |
+ 足し算 2 + 8 =10 | |
- 引き算 10 - 2 = 8 | |
* 掛け算 2 x 5 = 10 | |
/ 割り算 3.2 / 2 →1.6 9/2 → 4 | |
% 割り算のあまり 9 % 2 → 1 |
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【代入演算子】:右から左に代入する演算子 | |
= 右辺を左辺に代入 a = 10 → a | |
+= 左辺と右辺を足してから左辺に代入 | |
-= 左辺から右辺を引き算し、左辺に代入 | |
*= 左辺と右辺を掛け算し、左に代入 | |
/= 左辺と右辺を割り算し、左に代入 | |
%= 左辺と右辺を割り算し、そのあまりを左に代入 | |
+= 左辺後ろに右を連結して代入 a += "腹筋" → a //(a =a+ "腹筋")と同じ |
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1 public class Muscle{ | |
2 public static void main(String[] args){ | |
3 String muscle = "15"; | |
4 int a = Integer.parseInt(muscle); | |
5 System.out.println("腹筋の回数は"+(muscle+100)+"回ですよ❤︎!!"); | |
6 } | |
7 } |
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【乱数を発生させる】 | |
int a = new java.util.Random().nextInt(1); | |
・1は発生させる乱数の値 | |
・1に1以上の整数を指定してこの命令を呼び出すと、0以上かつ1で指定した数字未満のランダムな整数がaに代入される | |
例 | |
1に100を代入すると、aには0〜99のいずれかが代入される |
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1 public class Muscle{ | |
2 public static void main(String[] args){ | |
3 int a = new java.util.Random().nextInt(100); | |
4 System.out.println("今日の腕立ての回数は"+a+"です!!"); | |
5 } | |
6 } |
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【キーボードから1行の文字列の入力を受け付ける命令】 | |
String input = new java.util.Scanner(System.in).nextLine(); | |
【キーボードから1つの整数の入力を受け付ける命令】 | |
int input = new java.util.Scanner(System.in).nextIn(); | |
・これらの文を実行すると、プログラムは一時停止となり、ユーザーがキーボードから文字入力できる | |
・入力後、入力内容が変数inputに代入される | |
・nextLine()は文字列を受け取る | |
・nextInt()は数字の入力を受け取る |
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1 public class Muscle{ | |
2 public static void main(String[] args){ | |
3 System.out.println("名前を入力してください!"); | |
4 String name = new java.util.Scanner(System.in).nextLine(); | |
5 System.out.println("年齢を入力してください!!"); | |
6 int age = new java.util.Scanner(System.in).nextInt(); | |
7 System.outprintln("Welcome!"+age+"歳の"+name+"さん!"); | |
8 } | |
9 } |
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【インクリメントとデクリメント演算子】:変数の内容を1だけ増やしたり減らしたりする場合 | |
++ 値を1増やす | |
-- 値を1減らす |
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1 public class MuscleWorld{ | |
2 public static void main(String[] args){ | |
3 int a = 10; | |
4 a++; /*aの内容が1増える*/ | |
5 System.out.println(a); | |
6 } | |
7 } |
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【命令実行の文】 | |
呼び出す命令の名前(引数); |
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【改行せずに画面に文字を入力する】 | |
System.out.print(1); | |
/*画面に1を表示するが、改行せずに画面に表示されます*/ |
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1 public class Muscle{ | |
2 public static void main(String[] args){ | |
3 String niku = "腹斜筋"; | |
4 System.out.print("私のチャームポイントは"); | |
5 System.out.print(niku); | |
6 System.out.print("です!"); | |
7 } | |
8 } |
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【2つの値を比較して大きいほうの数字を代入する命令】 | |
int p( = Math.max(1,2); | |
/*1or2は比較したい値や式。大きいほうの値がpに代入される。変数pはp以外でもOK*/ |
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1 public class Muscle{ | |
2 public static void main(String[] args){ | |
3 int a = 10; | |
4 int b = 5; | |
5 int p = Math.max(a,b); | |
6 System.out.println("比較:"+a+"と"+b+"とで大きいほうは"+p); | |
7 } | |
8 } |
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【文字列を数字に変換する命令】 | |
int a = Integer.parseInt(1); | |
/*1は数字として解釈させたい文字列("10")など*/ |
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