Java常用类06：Math、UUID类

Math类

public class Hello{
    public static void main(String[] args) {
        //常量E和PI
        System.out.println(Math.E);
        System.out.println(Math.PI);
        //1.绝对值函数abs()
        System.out.println(Math.abs(-10));
        //2.三角函数cos()、sin()、tan()、acos()、asin()、atan()
        System.out.println(Math.acos(-1.0));
        //3.开平方函数sqrt()
        System.out.println(Math.sqrt(4.0));
        //4.最值函数max()、min()
        System.out.println(Math.max(1, 2));
        //5.对数函数log()
        System.out.println(Math.log(10));
        //6.幂函数exp()、pow()
        System.out.println(Math.exp(2));
        System.out.println(Math.pow(2, 3));
        //7.随机数函数random()
        System.out.println(Math.random());
        //8.向上取整函数ceil()
        System.out.println(Math.ceil(1.5));
        //9.四舍五入round()
        System.out.println(Math.round(1.5));
    }
}

UUID类

import java.util.UUID;

public class Hello{
    public static void main(String[] args) {
        //生成全局唯一标识符
        UUID uuid = UUID.randomUUID();
        String str = uuid.toString();
        System.out.println(str);
    }
}