Math常用方法

round()

/*四舍五入的原理是在参数上加0.5然后做向下取整。*/
    @Test
    public void round(){
        System.out.println(Math.round(1.5));//1.5+0.5=2 结果2
        System.out.println(Math.round(-1.5));//-1.5+0.5=-1 结果-1
        System.out.println(Math.round(1.9));//1.9+0.5=2.4 结果2
        System.out.println(Math.round(-1.9));//-1.9+0.5=-1.4 结果-2
        System.out.println(Math.round(1.8));//1.8+0.5=2.3 结果2
        System.out.println(Math.round(-1.8));//-1.8+0.5=-1.3 结果-2
        System.out.println(Math.round(1.1));//1.1+0.5=1.6 结果1
        System.out.println(Math.round(-1.1));//-1.1+0.5=-0.6 结果-1
        System.out.println(Math.round(1.4));//1.4+0.5=1.9 结果1
        System.out.println(Math.round(-1.4));//-1.4+0.5=-0.9 结果-1
    }