数 函数类 Math类

Math样式:

    //1.获取圆周率π
        double pi = Math.PI;
        System.out.println(pi);//3.141592653589793
        
    //2.获取绝对值 abs  结果都是正值
        double abs = Math.abs(-5.5);    
        System.out.println(abs);    
    //3.  天花板、地板砖    
    // ceil(double d)  结果值比参数大的最小整数的double值（往上取整）
        double ceil = Math.ceil(-3.4);
        System.out.println(ceil);  //-3.0
    //  floor (double d)结果值比参数小的最大整数的double值（往下取整）
        double floor = Math.floor(-3.9);
        System.out.println(floor);//-4
    //4.max(double a,double b)和 min(double a,double b)
        double max = Math.max(3.9,5.4);
        System.out.println(max);//5.4
        double min = Math.min(3.9,5.4);
        System.out.println(min);//3.9
    //5.pow(a,b)获取a的b次幂的值   a^b  -->  2^3 =2*2*2=8
        double pow = Math.pow(2, 3);
        System.out.println(pow);//8.0
    //6. round(double a) 正数四舍五入  负数六舍五入
        long round = Math.round(3.5);// -3.5  -3.6
        System.out.println(round);//4   -4     -3
    //7.random()  获取随机数  [0.0,1.0)小数
        double random = Math.random();
        System.out.println(random);
        //获取[5,100]
        int ranNum = (int)(Math.random()*(100-5+1))+5;
        System.out.println(ranNum);