Java 基础(算术运算符, 赋值运算符)

运算符:算术运算符

运算符	运算	范例	结果
+	正号	+3	3
-	负号	b=4;-b	-4
+	加	5+5	10
-	减	6-4	2
*	乘	3*4	12
/	除	5/5	1
%	取模（取余）	7%5	2
++	自增（前）：先运算后取值	a=2;b=++a;	a=3;b=3
++	自增（后）：先取值后运算	a=2;b=a++;	a=3;b=2
--	自减（前）：先运算后取值	a=2;b=--a;	a=1;b=1
--	自减（后）：先取值后运算	a=2;b=a--;	a=1;b=2
+	字符串连接	"He"+"llo"	"Hello"

class AriTest{
    public static void main(String[] args){
        //除号
        int num1 = 12;
        int num2 = 5;
        int result1 = num1 / num2;
        System.out.println(result1);  //2
        
        int result2 = num1 / num2 * num2;
        System.out.println(result2);  //10
        
        double result3 = num1 / num2;
        System.out.println(result3);  //2.0
    
        double result4 = num1 / (num2 + 0.0);
        System.out.println(result4);  //2.4
        
        double result5 = (double)num1 / num2;
        System.out.println(result5);  //2.4
        
        // % 取余运算
        // 结果的负号与被模数的符号相同
        // 开发中，经常使用%来判断能否被除尽的情况。
        int m1 = 12;
        int n1 = 5;
        System.out.println("m1 % n1 = "+ m1 % n1);  //2
        
        int m2 = -12;
        int n2 = 5;
        System.out.println("m2 % n2 = "+ m2 % n2);  //-2
        
        int m3 = 12;
        int n3 = -5;
        System.out.println("m3 % n3 = "+ m3 % n3);  //2
        
        int m4 = -12;
        int n4 = -5;
        System.out.println("m4 % n4 = "+ m4 % n4);  //-2
        
        //(前)++: 先自增1，后运算
        //(后)++: 先运算，后自增1
        int a1 = 10;
        int b1 = ++a1;
        System.out.println("a1 = " + a1 + ",b1 = " +b1); // a1 = 11, b1 = 11
        
        int a2 = 10;
        int b2 = a2++;
        System.out.println("a2 = " + a2 + ",b2 = " +b2); // a2 = 11, b2 = 10
        
        short s1 = 10;
        //s1 = s1 + 1; //编译失败
        //s1 = (short)(s1 + 1); //编译正确
        s1++;                   // 自增1不会改变本身变量的数据类型
        System.out.println(s1); // 11
    }
}

class AriExer{
    public static void main(String[] args){
        int num = 187;
        
        int bai = num / 100;
        int shi = num % 100 / 10;
        int ge  = num % 10; 
        
        System.out.println("百位为: " + bai);  //百位为: 1
        System.out.println("十位为: " + shi);  //十位为: 8
        System.out.println("个位为: " + ge);   //个位为: 7
    }
}

运算符：赋值运算符

符号: =

• 当 "=" 两侧数据类型不一致时，可以使用自动类型转换或使用强制类型转换原则进行处理。
• 支持连续赋值

扩展赋值运算符：+=, -=, *=, /=, %=

class SetValueTest {
    public static void main(String[] args) {
        //赋值符号：=
        int i1 = 10;
        int j1 = 10;
        
        //连续赋值
        int i2, j2;
        i2 = j2 = 10;
        
        int num1 = 10;
        num1 += 2;
        System.out.println(num1);   //12
        
        int num2 = 12;
        num2 %= 5;
        System.out.println(num2);   //2
        
        short s1 = 10;
        //s1 = s1 + 2;   //编译失败
        s1 += 2;
        System.out.println(s1);     //12 
    }
}