int num;

num = 10 + 4;   // num = 14
num = 9 - 2;    // num = 7
num = 3 * 8;    // num = 24
num = 7 / 3;    // num = 2
num = 7 % 3;    // num = 1

浮動小数点数に対する演算

double d;

d = 10 / 8       // d = 1.0
d = 10.0 / 8;    // d = 1.25
d = 10 / 8.0;    // d = 1.25
d = 10.0 / 8.0;  // d = 1.25

サンプルプログラム

class JSample1_1{
  public static void main(String args[]){
    System.out.println(10 + 4);
    System.out.println(9 - 2);
    System.out.println(3 * 8);
    System.out.println(7 / 3);
    System.out.println(7 % 3);

    double d;

    d = 10 / 8;
    System.out.println(d);
    d = 10.0 / 8.0;
    System.out.println(d);
  }
}

[xxxxxxxx@dddddddddd Ope]$ java JSample1_1
14
7
24
2
1
1.0
1.25
[xxxxxxxx@dddddddddd Ope]$ 

int n1, n2, n3;

n1 = 10;
n2 = -n1;    // n2 = -10

n3 = -8

int n1, n2;

n1 = 10;
n2 = +n1;    // n2 = 10

サンプルプログラム

class JSample2_1{
  public static void main(String args[]){
    int n1, n2;

    n1 = 10;
    n2 = - n1;
    System.out.println(n2);

    n2 = + n1;
    System.out.println(n2);
  }
}

[xxxxxxxx@dddddddddd Ope]$ java JSample2_1
-10
10
[xxxxxxxx@dddddddddd Ope]$ 

除算

サンプルプログラム

class JSample3_1{
  public static void main(String args[]){
    int n;

    n = 3 / 0;
    System.out.println(n);
  }
}

[xxxxxxxx@dddddddddd Ope]$ java JSample3_1
Exception in thread "main" java.lang.ArithmeticException: / by zero
	at JSample3_1.main(JSample3_1.java:5)
[xxxxxxxx@dddddddddd Ope]$ 

サンプルプログラム

class JSample3_2{
  public static void main(String args[]){
    double d;

    d = 3.1 / 0;
    System.out.println(d);

    d = 3 / 0.0;
    System.out.println(d);

    d = -3.1 / 0;
    System.out.println(d);
  }
}

[xxxxxxxx@dddddddddd Ope]$ java JSample3_2
Infinity
Infinity
-Infinity
[xxxxxxxx@dddddddddd Ope]$ 

剰余

サンプルプログラム

class JSample3_3{
  public static void main(String args[]){
    int n;

    n = 3 % 0;
    System.out.println(n);
  }
}

[xxxxxxxx@dddddddddd Ope]$ java JSample3_3
Exception in thread "main" java.lang.ArithmeticException: / by zero
	at JSample3_3.main(JSample3_3.java:5)
[xxxxxxxx@dddddddddd Ope]$ 

サンプルプログラム

class JSample3_4{
  public static void main(String args[]){
    double d;

    d = 3.1 % 0;
    System.out.println(d);

    d = 3 % 0.0;
    System.out.println(d);

    d = -3.1 % 0;
    System.out.println(d);
  }
}

[xxxxxxxx@dddddddddd Ope]$ java JSample3_4
NaN
NaN
NaN
[xxxxxxxx@dddddddddd Ope]$ 

int num;
num = 10 + 5 * 4;

1) 10 + 5 = 15
2) 15 * 4 = 60
3) num = 60

1) 5 * 4 = 20
2) 10 + 20 = 30
3) num = 30

優先順位 高い
------------------------------------------------
左  (引数)  [配列添字]  .  ++  --(後置き)
右  !  ~  +  - (単項演算子)  ++  --(前置き)
右  new  (型)
左  *  /  %
左  +  - (算術演算子)
左  <<  >>  >>>
左  >  >=  <  <=  instanceof
左  ==  !=
左  &
左  ^
左  |
左  &&
左  ||
右  ?:
右  =  ope=
 ------------------------------------------------
優先順位 低い

int num;
num = 10 + 5 * 4;

int num;
num = 10 + 5 - 4;

サンプルプログラム

class JSample4_1{
  public static void main(String args[]){
    int n1, n2;

    n1 = 10 * 5 + 4;
    n2 = 4 + 10 * 5;
    System.out.println(n1);
    System.out.println(n2);
  }
}

[xxxxxxxx@dddddddddd Ope]$ java JSample4_1
54
54
[xxxxxxxx@dddddddddd Ope]$ 

int num;
num = 10 + 5 * 4;

int num;
num = (10 + 5) * 4;

int num;
num = (10 + 8 / 2) * 4;

int num;
num = ((10 + 8) / 2) * 4;

サンプルプログラム

class JSample5_1{
  public static void main(String args[]){
    int num;

    num = 10 + 8 / 2 * 4;
    System.out.print("10 + 8 / 2 * 4 = ");
    System.out.println(num);

    num = (10 + 8 / 2) * 4;
    System.out.print("(10 + 8 / 2) * 4; = ");
    System.out.println(num);

    num = ((10 + 8) / 2) * 4;
    System.out.print("((10 + 8) / 2) * 4 = ");
    System.out.println(num);
  }
}

[xxxxxxxx@dddddddddd Ope]$ java JSample5_1
10 + 8 / 2 * 4 = 26
(10 + 8 / 2) * 4; = 56
((10 + 8) / 2) * 4 = 36
[xxxxxxxx@dddddddddd Ope]$ 

int num = 7;
num = num + 1;

int num = 7;
num++;

int num = 7;
num--;

サンプルプログラム

class JSample6_1{
  public static void main(String args[]){
    int num;

    num = 10;
    System.out.println(num);

    num++;
    System.out.println(num);

    num++;
    System.out.println(num);

    num--;
    System.out.println(num);
  }
}

[xxxxxxxx@dddddddddd Ope]$ java JSample6_1
10
11
12
11
[xxxxxxxx@dddddddddd Ope]$ 

前置:  ++変数
後置:  変数++

前置:  --変数
後置:  変数--

int a = 7;

a++;
System.out.println(a);    // 8

++a;
System.out.println(a);    // 9

前置と後置で結果が異なる場合

int a = 7;
int b;

b = a++;
System.out.println(a);
System.out.println(b);

int a = 7;
int b;

b = a;
a = a + 1;
System.out.println(a);    // 8
System.out.println(b);    // 7

int a = 7;
int b;

b = ++a;
System.out.println(a);
System.out.println(b);

int a = 7;
int b;

a = a + 1;
b = a;
System.out.println(a);    // 8
System.out.println(b);    // 8

サンプルプログラム

class JSample7_1{
  public static void main(String args[]){
    int num;

    System.out.println("後置の場合");

    num = 10;
    System.out.println(num++);
    System.out.println(num);

    System.out.println("前置の場合");

    num = 10;
    System.out.println(++num);
    System.out.println(num);
  }
}

[xxxxxxxx@dddddddddd Ope]$ java JSample7_1
後置の場合
10
11
前置の場合
11
11
[xxxxxxxx@dddddddddd Ope]$ 

0x3F30A5A5

0011 1111 0011 0000 1010 0101 1010 0101
---- ---- ---- ---- ---- ---- ---- ----
 3    F    3    0    A    5    A    5

ビットAND

byte b;
b = 0x55 & 0x0F;

01010101  = 0x55
00001111  = 0x0F
--------
00000101  = 0x05

ビットOR

byte b;
b = 0x55 | 0x0F;

01010101  = 0x55
00001111  = 0x0F
--------
01011111  = 0x5F

ビットXOR

byte b;
b = 0x55 ^ 0x0F;

01010101  = 0x55
00001111  = 0x0F
--------
01011010  = 0x5A

ビットNOT

byte b;
b = ~0x55;

01010101  = 0x55
--------
10101010  = 0xAA

サンプルプログラム

class JSample8_1{
  public static void main(String args[]){
    byte b;

    b = 0x55 & 0x0F;
    System.out.print("0x55 & 0x0F = ");
    System.out.printf("0x%02x\n", b);

    b = 0x55 | 0x0F;
    System.out.print("0x55 | 0x0F = ");
    System.out.printf("0x%02x\n", b);

    b = 0x55 ^ 0x0F;
    System.out.print("0x55 ^ 0x0F = ");
    System.out.printf("0x%02x\n", b);

    b = ~0x55;
    System.out.print("~0x55 = ");
    System.out.printf("0x%02x\n", b);
  }
}

[xxxxxxxx@dddddddddd Ope]$ java JSample8_1
0x55 & 0x0F = 0x05
0x55 | 0x0F = 0x5f
0x55 ^ 0x0F = 0x5a
~0x55 = 0xaa
[xxxxxxxx@dddddddddd Ope]$ 

左シフト

byte b;
b = 0x15 << 2;

00010101  = 0x15
--------
00101010  = 左へ1つシフト
01010100  = 左へ2つシフト

右シフト(符号有り)

byte b;
b = 0x2A >> 2;

10100011  = 0xA3
--------
11010001  = 右へ1つシフト
11101000  = 右へ2つシフト

右シフト(符号無し)

byte b;
b = 0xA3 >>> 2;

10100011  = 0xA3
--------
01010001  = 右へ1つシフト
00101000  = 右へ2つシフト

サンプルプログラム

class JSample9_1{
  public static void main(String args[]){
    byte b;

    b = 8 << 3;
    System.out.print("8 << 3 = ");
    System.out.println(b);

    b = -10 << 2;
    System.out.print("-10 << 2 = ");
    System.out.println(b);

    b = 8 >> 1;
    System.out.print("8 >> 1 = ");
    System.out.println(b);

    b = -20 >> 2;
    System.out.print("-20 >> 2 = ");
    System.out.println(b);
  }
}

[xxxxxxxx@dddddddddd Ope]$ java JSample9_1
8 << 3 = 64
-10 << 2 = -40
8 >> 1 = 4
-20 >> 2 = -5
[xxxxxxxx@dddddddddd Ope]$ 

int num;

num = 10;
num = num + 8;

int num;

num = 10;
num += 8;

多重代入

変数1 = 変数2 = 変数3 = 値;

変数3 = 値;
変数2 = 変数3;
変数1 = 変数2;

変数1 += 変数2 *= 変数3 = 値;

変数3 = 値;
変数2 = 変数2 * 変数3;
変数1 = 変数1 + 変数2;

サンプルプログラム

class JSample10_1{
  public static void main(String args[]){
    int num;

    num = 10;
    System.out.println(num);

    num += 5;
    System.out.println(num);

    num *= 2;
    System.out.println(num);

    num /= 3;
    System.out.println(num);
  }
}

[xxxxxxxx@dddddddddd Ope]$ java JSample10_1
10
15
30
10
[xxxxxxxx@dddddddddd Ope]$ 

int old = 10;

if (old >= 20){
  System.out.println("20歳以上です");
}else{
  System.out.println("20歳未満です");
}

左辺 関係演算子 右辺
^^^^^^^^^^^^^^^^^^^^
式が評価され、結果として式がtrueかfalseとなる

大小の比較

左辺 < 右辺
左辺 <= 右辺
左辺 > 右辺
左辺 >= 右辺

int num = 10;
boolean b1, b2;

b1 = num > 5;
b2 = num <= 4;

等しいかどうかの比較

左辺 == 右辺
左辺 != 右辺

int num = 10;
boolean b1, b2;

b1 = num == 5;
b2 = num != 4;

サンプルプログラム

class JSample11_1{
  public static void main(String args[]){
    int num = 10;

    System.out.println("num = " + num);

    System.out.print("num > 5  --> ");
    System.out.println(num > 5);

    System.out.print("num <= 4  --> ");
    System.out.println(num <= 4);

    System.out.print("num == 5  --> ");
    System.out.println(num == 5);

    System.out.print("num != 4  --> ");
    System.out.println(num != 4);
  }
}

[xxxxxxxx@dddddddddd Ope]$ java JSample11_1
num = 10
num > 5  --> true
num <= 4  --> false
num == 5  --> false
num != 4  --> true
[xxxxxxxx@dddddddddd Ope]$ 

論理積

左辺 && 右辺

int num = 10;
boolean b;

b = num > 5 && num <= 20;

論理和

左辺 || 右辺

int num1 = 10;
int num2 = 20;
boolean b;

b = num1 > 20 || num2 < 30;

int num1 = 30;
int num2 = 10;
boolean b;

b = num1 > 20 || num2 < 30 && num2 %gt; 20;

論理否定

!右辺

int num = 10;
boolean b;

b = !(num > 20);

判定される順番

左辺 && 右辺

左辺 || 右辺

int num1 = 30;
int num2 = 25;
boolean b;

b = num1 > 10 || ++num2 < 40;

サンプルプログラム

class JSample12_1{
  public static void main(String args[]){
    int num = 30;

    System.out.println("num = " + num);

    System.out.print("num > 5 && num < 20  --%gt; ");
    System.out.println(num > 5 && num < 20);

    System.out.print("num > 20 || num < 10  --> ");
    System.out.println(num > 20 || num < 10);

    System.out.print("!(num < 20)  --> ");
    System.out.println(!(num < 20));
  }
}

[xxxxxxxx@dddddddddd Ope]$ java JSample12_1
num = 30
num > 5 && num < 20  --> false
num > 20 || num < 10  --> true
!(num < 20)  --> true
[xxxxxxxx@dddddddddd Ope]$ 

条件式 ? 式1 : 式2

char c;
int num;

num = 20;
c = num >= 0 ? '正' : '負';

サンプルプログラム

class JSample13_1{
  public static void main(String args[]){
    char c;
    int num;

    num = 20;
    c = num >= 0 ? '正' : '負';
    System.out.print(num + "は");
    System.out.println(c);

    num = -4;
    c = num >= 0 ? '正' : '負';
    System.out.print(num + "は");
    System.out.println(c);
  }
}

[xxxxxxxx@dddddddddd Ope]$ java JSample13_1
20は正
-4は負
[xxxxxxxx@dddddddddd Ope]$ 

文字列1 + 文字列2

System.out.println("目覚まし" + "時計");

文字列と数値の連結

System.out.println("200" + 9);

System.out.println("200" + "9");

文字列連結の順序

System.out.println(100 + 80 + "$");

System.out.println("$" + 100 + 80);

System.out.println("$" + (100 + 80));

サンプルプログラム

class JSample14_1{
  public static void main(String args[]){
    System.out.println(200 + 9);
    System.out.println("200" + 9);
    System.out.println(200 + "9");
    System.out.println("200" + "9");

    System.out.println(100 + 80 + "$");
    System.out.println("$" + 100 + 80);
    System.out.println("$" + (100 + 80));
  }
}

[xxxxxxxx@dddddddddd Ope]$ java JSample14_1
209
2009
2009
2009
180$
$10080
$180
[xxxxxxxx@dddddddddd Ope]$