常见对象_Math类概述和方法使用

package cn.itcast_01;

/*
 * Math:用于数学运算的类。
 * 成员变量:
 *     public static final double PI:π圆周率
 *   public static final double E:自然对数
 * 成员方法:
 *     public static int abs(int a):绝对值
 *     public static double ceil(double a):向上取整
 *     public static double floor(double a):向下取整
 *     public static int max(int a,int b):最大值
 *     public static int min(int a,int b):最小值
 *     public static double pow(double a,double b):a的b次幂
 *     public static double random():随机数[0.0,0.1](包左不包右)
 *     public static int round(float a):四舍五入(int接收a+0.5)
 *     public static long round(double a):四舍五入(long接收a+0.5)
 *     public static double sqrt(double a):正平方根
 */
public class MathDemo {
  public static void main(String[] args) {
    // public static final double PI
    System.out.println("PI:" + Math.PI);
    // public static final double E
    System.out.println("E:" + Math.E);
    System.out.println("----------------");

    // public static int abs(int a):绝对值
    System.out.println("abs:" + Math.abs(10));
    System.out.println("abs:" + Math.abs(-10));
    System.out.println("----------------");

    // public static double ceil(double a):向上取整
    System.out.println("ceil:" + Math.ceil(12.34));
    System.out.println("ceil:" + Math.ceil(12.56));
    System.out.println("----------------");

    // public static double floor(double a):向下取整
    System.out.println("floor:" + Math.floor(12.34));
    System.out.println("floor:" + Math.floor(12.56));
    System.out.println("----------------");

    // public static int max(int a,int b):最大值
    System.out.println("max:" + Math.max(12, 23));
    // 需求:我要获取三个数据中的最大值
    // 方法的嵌套调用
    System.out.println("max:" + Math.max(Math.max(12, 23), 18));
    // 需求:我要获取四个数据中的最大值
    System.out.println("max:"
        + Math.max(Math.max(25, 12), Math.max(15, 45)));

    // public static int min(int a,int b):最小值
    System.out.println("min:" + Math.min(12, 23));
    // 需求:我要获取三个数据中的最小值
    // 方法的嵌套调用
    System.out.println("min:" + Math.min(Math.min(12, 23), 18));
    // 需求:我要获取四个数据中的最小值
    System.out.println("min:"
        + Math.min(Math.min(25, 12), Math.min(15, 45)));
    System.out.println("----------------");

    // public static double pow(double a,double b):a的b次幂
    System.out.println("pow:" + Math.pow(2, 3));
    System.out.println("----------------");

    // public static double random():随机数[0.0,0.1](包左不包右)
    System.out.println("random:" + Math.random());
    // 获取一个1-100之间的随机数
    System.out.println("random:" + (int) ((Math.random() * 100) + 1));
    System.out.println("----------------");

    // public static int round(float a):四舍五入(int接收)
    System.out.println("round:" + Math.round(12.34f));
    System.out.println("round:" + Math.round(12.56f));
    System.out.println("----------------");

    // public static long round(double a):四舍五入(long接收)
    System.out.println("round:" + Math.round(12.34));
    System.out.println("round:" + Math.round(12.56));
    System.out.println("----------------");
    
    // public static double sqrt(double a):正平方根
    System.out.println("sqrt:"+Math.sqrt(4));

  }
}