情報処理技法（Javaプログラミング）I

1: class Main {
2:   public static void main(String[] args) {
3:     System.out.println("Hello World");
4:   }
5: }

1: #include <stdio.h>
2: void main() {
3:   printf("Hello World\n");
4: }

1: print('Hello World')

1: p "Hello World"

1: class Main {
2:   public static void main(String[] args) {
3:     System.out.println("Hello World");
4:   }
5: }

1: class Main {
2:   public static void main(String[] args) {
3:     System.out.println("JavaプログラムI");
4:   }
5: }

1: class Main {
2:   public static void main(String[] args) {
3:     System.out.println("情報処理技法");
4:     System.out.println(1 + 2);
5:     System.out.println(Math.PI);
6:     System.out.println(new StringBuilder("情報処理技法").reverse());
7:   }
8: }

 1: class Main {
 2:   public static void main(String[] args) {
 3:     // この行はコメント
 4: 
 5:     /*
 6:       この
 7:       範囲は
 8:       コメント
 9:     */
10: 
11:     // System.out.println("表示されません");
12:     // System.out.println("これも表示されません");
13:   }
14: }

# comment
a = 1  # comment

# comment
p 123

=begin
p 'ABC'
p 'DEF'
=end

p 456 # comment

//  1   2   3
{
    System.out.println("block1");
}
{
    System.out.println("block2");
}
{
    System.out.println("block3");
    {
        System.out.println("block3-1");
    }
    {
        System.out.println("block3-2");
    }
}
{
    System.out.println("block4");
    {
        System.out.println("block4-1");
        {
            System.out.println("block4-1-1");
        }
        {
            System.out.println("block4-1-2");
            {
                System.out.println("block4-1-2-1");
            }
        }
    }
    {
        System.out.println("block4-2");
    }
}

1: {System.out.println("block1");}{System.out.println("block2");}{System.out.println("block3");{System.out.println("block3-1");}{System.out.println("block3-2");}}{System.out.println("block4");{System.out.println("block4-1");{System.out.println("block4-1-1");}{System.out.println("block4-1-2");{System.out.println("block4-1-2-1");}}}{System.out.println("block4-2");}}

int i;        // 整数型のiという変数を宣言
double pi;    // 倍精度実数型のpiという変数を宣言
char ch;      // 文字型のchという変数を宣言
boolean flag; // 真偽値型のflagという変数を宣言

int i,j;
double x,y,z;

System.out.println(ch); // Error!

int class;      // classは予約語
double public;  // publicは予約語
boolean static; // staticは予約語

int i;                 // 整数型の変数iを宣言
i = 27;                // 変数iに27を代入
System.out.println(i); // 変数iを参照

int x = 0;             // 変数xを宣言し初期化
System.out.println(x); // 変数xを参照できる

int x;                 // 変数xを宣言して初期化しない
System.out.println(x); // 変数xを参照 -> Error!

int x;                 // 変数xを宣言して初期化しない
x = -1;                // 代入をすれば、
System.out.println(x); // 変数xを参照 -> OK

double pi = 3.14;       // 変数piを宣言し初期化
System.out.println(pi); // 変数piを参照できる

boolean flag = true;      // 変数flagを宣言し初期化
System.out.println(flag); // 変数flagを参照できる

byte   b = 3;
int    i = -11;
long   l = 1245678901234567890L;
float  f = 9.80665F;     // 標準重力加速度（m/s^2）
double d = 2.99792458E8; // 真空中の高速（m/s）

System.out.println(b);
System.out.println(i);
System.out.println(l);
System.out.println(f);
System.out.println(d);

char ch = '字';
boolean flag = true;

System.out.println(ch);
System.out.println(flag);

int i = 0;             // 変数iを宣言し初期化
System.out.println(i); // 変数i = 0
i = 1;                 // 変数iに代入
System.out.println(i); // 変数i = 1
i = 2;                 // 変数iに代入
System.out.println(i); // 変数i = 2

double x, y, z;
x = y = z = 12.345;
System.out.println(x);
System.out.println(y);
System.out.println(z);

int i = 0;             // 変数iを宣言し初期化
System.out.println(i); // 変数i = 0
int i = 1;             // 変数iを再び宣言 -> Error!!
System.out.println(i); // 変数i = 1

{
    int i = 0;             // 変数iを宣言し初期化
    System.out.println(i); // 変数i = 0
}
{
    int i = 1;             // 変数iを再び宣言 -> OK
    System.out.println(i); // 変数i = 1
}

{
    int out;
    {
        out = 10;
        System.out.println(out);
    }
}

{
    int out;
    {
        out = -3;
    }
    System.out.println(out);
}

{
    {
        int in = -10;
    }
    System.out.println(in); // Error!!
}

1: {
2:     int x = 1;
3:     {
4:         int x = -1 // Error!!
5:         System.out.println(x);
6:     }
7:     System.out.println(x);
8: }

double π = 3.14;
System.out.println(π);
int 日本語 = 10;
System.out.println(日本語);
// int 😜❤🤷 = -99; // Error!!

System.out.println(1 + 2);

System.out.println(3);

int x = 123;
System.out.println(x);

System.out.println(123);

System.out.println(1 + 2);
System.out.println(3 - 4);
System.out.println(5 * 6);

System.out.println(5 / 3); // 商
System.out.println(5 % 3); // 余

System.out.println(43871028 / 732); // 商
System.out.println(43871028 % 732); // 余
System.out.println(59933 * 732 + 72); // 検算

System.out.println(2 * 3.14 * 5.7);
System.out.println(0.1 + 0.9);
System.out.println(2 - (1.9 + 3.2));
System.out.println(6.+.6);

System.out.println(5.0 / 3);
System.out.println(2 / .037);
System.out.println(1e+7 / 10); // 1e+7 = 10,000,000

System.out.println(5 / 3);
System.out.println(5 % 3);

System.out.println(5.0 / 3);
System.out.println(5D / 3);
System.out.println(5F / 3);

System.out.println(5.0 % 2.5);

int height = 7;
int width = 3;
int area = height * width;
System.out.println(area);

int x = 5;
System.out.println(x);
x = x * 7;
System.out.println(x);

int i = 3;
System.out.println(i);
i ++; // i = i + 1
System.out.println(i);
i --; // i = i - 1
System.out.println(i);

// helloWorldILoveYou = helloWorldILoveYou + 1;
// helloWorldILoveYou ++;

int i = 3;
System.out.println(i);
i += 2; // i = i + 2;
System.out.println(i);
i -= 1; // i = i - 1;
System.out.println(i);
i *= 3; // i = i * 3;
System.out.println(i);
i /= 4; // i = i / 4;
System.out.println(i);

System.out.println(!true);
System.out.println(!false);

System.out.println(true && true);
System.out.println(true && false);
System.out.println(false && true);
System.out.println(false && false);

System.out.println(true || true);
System.out.println(true || false);
System.out.println(false || true);
System.out.println(false || false);

boolean f1 = true;
boolean f2 = false;
System.out.println( !f1);
System.out.println( f1 && f2);
System.out.println( f1 || f2);

System.out.println( 3 == 3 );
System.out.println( 3 == 5 );
System.out.println( true == true);
System.out.println( true == false);

System.out.println( 3 != 3 );
System.out.println( 5 != 5 );
System.out.println( true != true);
System.out.println( true != false);

System.out.println( 2 < 3 );
System.out.println( 2 < -3 );

System.out.println( 2 <= 3 );
System.out.println( 2 <= -3 );

System.out.println( 2 > 3 );
System.out.println( 2 > -3 );

System.out.println( 2 >= 3 );
System.out.println( 2 >= -3 );

int i = 8;
int j = -3;
System.out.println( i == 8);
System.out.println( i + j == 5);
System.out.println( i < 10);
System.out.println( i >= j);

boolean flag = 3 < 5;
System.out.println(flag);

System.out.println(true == true );
System.out.println( 2 < 5 );
System.out.println(( 2 < 5 ) == true );

System.out.println((2 < 3) && ( 3 < 4));
System.out.println((2 < 3) || ( 3 <= 4));

int score = 95;
System.out.println(score > 60);

int average = (87 + 63 + 76 + 91) / 4;
System.out.println(average);
System.out.println(average >= 60);

System.out.println(! 10 > 5);

int i = 65536;
long l = i;
System.out.println(i);
System.out.println(l);

float f = 3.14F;
double d = f;
System.out.println(f); // 3.14
System.out.println(d); // 3.140000104904175

int i = 123456;
double d = i;
System.out.println(i); // 123456
System.out.println(d); // 123456.0

char c = 'A';
int i = c;
System.out.println(i); // 65

short s = 654;
byte b = s; // Error!
System.out.println(s);
System.out.println(b);

double d = 3.14;
int i = d; // Error!
System.out.println(d);
System.out.println(i);

int i = 100;
byte b = (byte) i;
System.out.println(b);

// 00000000 ~ 11111111 (2進数)
// -128     ~ 127 (10進数)
// 11111111 + 1 = 100000000 (9bit)
int i = 128;
byte b = (byte) i;
System.out.println(b);

double pi = 3.14;
int i = (int) pi;
System.out.println(i);

double d = 1.0E36;
float f = (float)d;
System.out.println(f);

int i = 128;
byte b = (byte) i;
System.out.println(b); // -128

double d = 1.0E39;
float f = (float) d;
System.out.println(f); // Infinity

double d = 1.0E36;
int i = (int)d;
System.out.println(i); // 2147483647

int i = 66;
char c = (char)i;
System.out.println(c); // B

String str = "こんにちは";
System.out.println(str);

String str = "文字列";   // 変数strを宣言し初期化
System.out.println(str); // 変数strを参照できる

String str = ""; // 空文字列
System.out.println(str);

String str = null;
System.out.println(str);

String a = "Hello";
String b = "World";
String str = a + b;
System.out.println(str);

String a = "Hello";
String b = "World";
String space = " ";
String str = a + space + b;
System.out.println(str);

String a = "Hello";
String b = "World";
// System.out.println(a - b); // Error!!
// System.out.println(a * 2); // Error!!
// System.out.println(a / b); // Error!!

int a = 2750;
String b = "円";
String str = a + b;
System.out.println(str);

String a = "$";
double b = 3.75;
String str = a + b;
System.out.println(str);

char a = '$';
double b = 3.75;
String str = a + b; // Error

int x = 3 * 7;
System.out.println("3*7=" + x);

int  i = 3776;
char c = '㍍';
System.out.println("富士山の高さは" + i + c);

double pi = 3.1415926534;
String s1 = "π=";
String s2 = s1 + pi;
System.out.println(s2);

double pi = 3.1415926534;
String s1 = "" + pi;
System.out.println(s1);

char a = '$';
double b = 3.75;
double c = a + b;
System.out.println(c);

String s1 = "abc";
String s2 = "def";
String s3 = s1.concat(s2); // s1 + s2 と同じ意味
// String s3 = s2.concat(s1); // 結果が逆になる
System.out.println(s3);

String str1 = "ABC";
String str2 = "ABC";
System.out.println(str1.equals(str2));

String str1 = "あいうえお";
String str2 = "あいうえお";
String str3 = "あい";
str3 = str3 + "うえお";

System.out.println(str1 == str2);
System.out.println(str1 == str3);

System.out.println(str1.equals(str2));
System.out.println(str1.equals(str3));

String str = "あいうえお";
System.out.println(str.length());
str = "ふるいけやかわずとびこむみずのおと";
System.out.println(str.length());

String str = "あいうえお";
char ch = str.charAt(0); // char型
System.out.println(ch);

String str = "あいうえお";
char ch = str.charAt(5);
System.out.println(ch);

String str = "あいうえお";
String sub = str.substring(1);
System.out.println(sub);

String str = "０１２３４５６７８９";
String sub = str.substring(3, 6);
System.out.println(sub);

class Main {
  public static void main(String[] args) {
    double taijuu = 80.0;
    double shinchou = 1.7;

    double bmi = taijuu / (shinchou * shinchou);
    System.out.println("あなたのBMIは" + bmi + "です");
    System.out.println("普通体重？ = " + ((18.5 <= bmi) && (bmi < 25.0)));
  }
}

int[] iArray;
double[] dArray;
char[] chArray;
String[] strArray;

int[] iArray = {0, 1, 2, 3};
double[] dArray = {1, 1.414, 1.732, 2, 2.236};
char[] chArray = {'あ','い','う', 'A', 'B'};
String[] strArray = {"こんにちは", "さようなら", "ありがとう", "おやすみ"};

int[] iArray = {0, 1, 2, 3};
System.out.println(iArray[0]);
System.out.println(iArray[3]);

String[] strArray = {"こんにちは", "さようなら", "ありがとう", "おやすみ"};
System.out.println(strArray[2]);
System.out.println(strArray[3]);

double[] dArray = {1, 1.414, 1.732, 2, 2.236};
System.out.println(dArray[5]); // 実行時に例外
System.out.println(dArray[-1]); // 実行時に例外

char[] chArray = {'あ','い','う', 'A', 'B'};
chArray[1] = 'わ';
System.out.println(chArray[1]);

double[] dArray = {1, 1.414, 1.732, 2, 2.236};
int i = 0;
System.out.println(dArray[i]);
i++;
System.out.println(dArray[i]);

int[][] image = {{1,0,1},
                 {0,1,0},
                 {1,0,1}};
System.out.println(image[0][2]);
System.out.println(image[1][1]);

int[] array = {2, 3, 5, 7, 11, 13, 17, 19};
System.out.println(array.length);

int[][] image = {{1,0,1,0},
                 {0,1,0,1},
                 {1,0,1,1}};
System.out.println(image.length);
System.out.println(image[0].length);

int[] array = {2, 3, 5, 7, 11, 13, 17, 19};
System.out.println(Arrays.toString(array));

int[] array = {2, 3, 5, 7, 11, 13, 17, 19};
array[3] = 0;
System.out.println(Arrays.toString(array));

int[][] image = {{1,0,1,0},
                 {0,1,0,1},
                 {1,0,1,1}};
System.out.println(Arrays.deepToString(image));

int a = 3;
int b = a * 4;
System.out.println(b);

{
    System.out.println("Block A");
}
{
    System.out.println("Block B");
}

double ransuu = Math.random();
System.out.println("乱数=" + ransuu);
int saikoro = ((int) (ransuu * 6)) + 1;
System.out.println("サイコロ=" + saikoro);

int saikoro = 0;
while (saikoro != 6) {
    double ransuu = Math.random();
    System.out.println("乱数=" + ransuu);
    saikoro = ((int) (ransuu * 6)) + 1;
    System.out.println("サイコロ=" + saikoro);
}

int terms = 100;

double pi = 0.0;
boolean positive = true;
for (int i = 0; i < terms; i++) {
    int divisor = 2 * i + 1;
    if (positive) {
        pi += 1.0 / divisor;
    } else {
        pi -= 1.0 / divisor;
    }
    positive = !positive;
}
pi *= 4;

System.out.println("Leibnizの公式 による円周率の近似値: " + pi);
System.out.println("Math.PI       による円周率の近似値: " + Math.PI);

long startTime = System.currentTimeMillis(); // ★

int n = 100;
boolean[] primes = new boolean[n + 1]; // 0〜nまでの配列を用意

for (int i = 2; i <= n; i++) {
    primes[i] = true;
}

for (int i = 2; i * i <= n; i++) {
    if (primes[i]) {
        for (int j = i * i; j <= n; j += i) {
            primes[j] = false;
        }
    }
}

long endTime = System.currentTimeMillis(); // ★
System.out.println("\n" + n +
                   "までの素数を求める計算にかかった時間は"
                   + (endTime - startTime) + "ミリ秒です。");

System.out.println("2 から " + n + " までの素数：");
for (int i = 2; i <= n; i++) {
    if (primes[i]) {
        System.out.print(i + " ");
    }
}