运算符之1 算术运算符

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运算符之1 算术运算符

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/*
运算符之一：算数运算符
+(正) -(负) +(加) -(减) *(乘) /(初) %(取余数) (前)++ (后)++ (前)-- (后)-- +(连接)



*/
class AriTest
{
	public static void main(String [] args)
	{
		//除号：/
		int num1 = 12;
		int num2 = 5;
		int result1 = num1/num2;//int之间做运算，结果还是int型  整型结果还是整型
		System.out.println(result1);//2

		int result2 = num1/num2*num2;
		System.out.println(result2);//10

		double result3 = num1/num2;//int运算完已经是2了，赋值给double后面加.0
		System.out.println(result3);//2.0

		double result4 = num1/num2 + 0.0;//2.0
		double result5 = num1/(num2 + 0.0);//2.4
		double result6 = (double)num1/num2;//2.4
		double result7 = (double)(num1/num2);//2.0
		System.out.println(result5);
		System.out.println(result6);


		//%:取余运算
		//结果的符号与被模数的符号相同 就是%前面的数
		//后面开发中经常使用%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，然后再运算
		//（后）++  先运算，后自增1       ***先写先加1，后写后加1
		int a1 = 10;
		int b1 = ++a1;
		System.out.println("a1 = " + a1 + ",b1 = " + b1);// 11 11

		
		int a2 = 10;
		int b2 = a2++;
		System.out.println("a2 = " + a2 + ",b2 = " + b2);// 11 10

		int a3 = 10;
		a3++;//++a3   (这么写没有区别)
		int b3 = a3;//11

		//注意点：
		short s1 = 10;
		//s1 = s1 + 1;不满足自动类型提升 编译失败
		//s1 = (short)(s1 + 1);//正确
		s1++;//自增1不会改变本身变量的数据类型
		System.out.println(s1);//11

		//问题
		byte bb1 = 127;
		bb1++;
		System.out.println("bb1 = " + bb1 );//-128


		//（前）--  先自-1，然后再运算
		//（后）--  先运算，后自-1       ***先写先-1，后写后-1
		int a4 = 10;
		int b4 = a4--;//int b4 = --a4;
		System.out.println("a4 = " + a4 + ",b4 = " + b4);

		








	}
}

练习

/*
练习 数字***情况下，
     让计算机输出个位，十位，百位

*/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);
		System.out.println("十位为:" + shi);
		System.out.println("个位为:" + ge);
	}
}