本質：a % b = a - a /b * b;

        int num1 = 10 % 3;//10-(10/3)*3==>10-3*3==>1
int num2 = -10 % 3;//-10-((-10)/3)*3==>-10-(-3)*3==>-1
int num3 = 10 % -3;//10-[(10)/(-3)]*(-3)==>10-(-3)*(-3)==>1
int num4 = -10 % -3;//-10-[(-10)/(-3)]*(-3)==>-10-3*(-3)==>-1

        System.out.println("num1="+num1);
System.out.println("num2="+num2);
System.out.println("num3="+num3);

System.out.println("num4="+num4);

        注意：當a或者b為double(小數)時;

例：double a = 10.2;

              double b = a%3;  //10.2-(10.2)/3*3 ==>10.2-概數(接近3.0的小數)*3 ==>10.2-概數(接近9.0的小數) ==>接近1.2的小數

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