System.out.println(Math.ceil(3.2));      //返回大于或等于給定數(shù)的整數(shù)
    System.out.println(Math.floor(3.8));     //返回小于或等于給定數(shù)的整數(shù)
    System.out.println(Math.round(3.5));     //四舍五入
    System.out.println(Math.abs(-45));       //絕對值
    System.out.println(Math.sqrt(64));       //算術(shù)平方根
    System.out.println(Math.pow(5,2));       //返回5的2次方

    System.out.println(Math.PI);
    System.out.println(Math.E);
    System.out.println(Math.random());       //返回0到1之間的隨機數(shù)