math.round的四舍六入五成双
数轴：-5 -4 -3 -2 -1 0 1 2 3 4 5就是括号内的数+0.5之后，向下取值 System.out.println("1.9:__"+Math.round(1.4));// 输出1.9:__1 System.out.println("1.8:__"+Math.round(1.3));// 输出1.8:__1 System.out.pri...
