java第十四次学习

简单类的用法

Math

public class JavaAPIDemo {
    public static void main(String[] args){
        System.out.println(Math.abs(-10.89));//绝对值
        System.out.println(Math.max(10.2,2.09));//取最大值
        System.out.println(Math.log(3));//取对数
        System.out.println(Math.round(18.8));//四舍五入
    }
}

Random

随机取数：

public class JavaAPIDemo {
    public static void main(String[] args){
        Random random = new Random();
        for (int i = 0; i < 10; i++) {
            System.out.print(random.nextInt(100)+",");//随机取数
        }
    }
}

40取7，且不重复

public class JavaAPIDemo {
    public static void main(String[] args){
        int data[] = new int[7];
        Random random = new Random();
        int foot = 0;
        while (foot<7){
            int num = random.nextInt(40);
            if(repeat(num,data)){
                data[foot++] = num;
            }
        }
        java.util.Arrays.sort(data);
        printArray(data);
    }
    public static void printArray(int temp[]){
        for(int x=0;x<temp.length;x++){
            System.out.print(temp[x] + ",");
        }
    }
    public static boolean repeat(int num,int temp[]){//判断是否重复
        if(num ==0){
            return false;
        }
        for (int i = 0; i < temp.length; i++) {
            if(num == temp[i]){
                return false;
            }
        }
        return true;
    }
}

Data日期处理类

public class JavaAPIDemo {
    public static void main(String[] args){
        Date date = new Date();
        System.out.println(date);//获取当前时间
    }
}