Java学习笔记（3）

运算符（2）

赋值运算符

运算符	描述
=	将右操作数的值赋给左侧操作数
+=	加和赋值操作符，它把左操作数和右操作数相加赋值给左操作数
-=	减和赋值操作符，它把左操作数和右操作数相减赋值给左操作数
*=	乘和赋值操作符，它把左操作数和右操作数相乘赋值给左操作数
/=	除和赋值操作符，它把左操作数和右操作数相除赋值给左操作数
%=	取模和赋值操作符，它把左操作数和右操作数取模后赋值给左操作数
<<=	左移位赋值运算符
>>=	右移位赋值运算符
&=	按位与赋值运算符
^=	按位异或赋值操作符
|=	按位或赋值操作符

例如

public class Test06 {
    public static void main(String[] args) {
        int a = 7;
        int b = 9;
        int c;
        c = a+b;
        System.out.println("c = a+b =" + c);
        c += a;
        System.out.println("c += a =" + c);
        c -= a;
        System.out.println("c -= a =" + c);
        c *= a;
        System.out.println("c *= a =" + c);
        c /= a;
        System.out.println("c /= a =" + c);
        c %= a;
        System.out.println("c %= a =" + c);
        c <<= a;
        System.out.println("c <<= a =" + c);
        c >>= a;
        System.out.println("c >>= a =" + c);
        c &= a;
        System.out.println("c &= a =" + c);
        c ^= a;
        System.out.println("c ^= a =" + c);
        c |= a;
        System.out.println("c |= a =" + c);
    }
}

运行结果如下

c = a+b =16
c += a =23
c -= a =16
c *= a =112
c /= a =16
c %= a =2
c <<= a =256
c >>= a =2
c &= a =2
c ^= a =5
c |= a =7

解析

• c = a+b =16将a+b的值赋给c
• c += a =23等价于c = c+a
• c -= a =16等价于c = c-a
• c *= a =16等价于c = c*a
• c /= a =16等价于c = c/a
• c %= a =16等价于c = c%a
• c <<= a =16等价于c = c<<a
• c >>= a =16等价于c = c>>a
• c &= a =16等价于c = c&a
• c ^= a =16等价于c = c^a
• c |= a =16等价于c = c|a

条件运算符

variable x = (expression) ? value if true : value if false

例如

public class Test07 {
    public static void main(String[] args) {
        int score = 70;
        //如果score >= 60成立，则grade为及格，否则为不及格
        String grade = (score >= 60) ? "及格":"不及格";
        System.out.println("grade = " + grade);

        int a = 7;
        int b = 9;
        int c;
        //如果 a>b 成立，则c=11，否则c=22
        c = (a > b) ? 11 : 22;
        System.out.println("Value of c =" + c);
    }
}

运行结果如下

grade = 及格
Value of c =22

运算符优先级

下表中优先级上行优先于下行

运算符说明	Java运算符
分隔符	. [] () {} , ;
单元运算符	++ -- ~ !
强制类型转换运算符	(type)
乘法、除法、求余	* / %
加法、减法	+ -
移位运算符	<< >> >>>
关系运算符	< <= > >= instanceof
等价运算符	== !=
换位与	&
换位异或	^
换位或	|
条件与	&&
条件或	||
条件运算符	?:
赋值运算符	= += -= *= /= &= |= ^= %= <<= >>= >>>=