四方法

4.4命令行传递参数

main方法也可以传递参数通过cmd 命令提示符运行先编译注意包的位置（回退）

public class Demo03 {
    public static void main(String[] args) {
        for (int i = 0; i < args.length; i++) {
            System.out.println(args[i]);
        }
    }
}

4.5 可变参数（不定项）

int。。。 i 只能在最后面

public class Demo04 {
    public static void main(String[] args) {
        Demo04 demo04 = new Demo04();
        demo04.test(1,3,4,5,6);
    }

    public static void test(int... i) {
        System.out.println(i[0]);
        System.out.println(i[1]);
        System.out.println(i[2]);
        System.out.println(i[3]);
    }
}

public class Demo05 {
    public static void main(String[] args) {
        printMax(1,32,44,3,666);

    }

    public static void printMax(double... numbers){
        if (numbers.length == 0){
            System.out.println("没有值传进来");
            return;
        }
        int i = 0;
        double result = numbers[0];
        for (i = 1; i < numbers.length; i++) {
            if (result < numbers[i]){
                result = numbers[i];
            }

        }
        System.out.println("数组中最大值是第" + i +"个" + result);
    }

4.6 递归

递归深度越大占用空间越多

public static void main(String[] args) {
        System.out.println(f(3));
    }
    public static int f(int n){
        if (n == 1) {
            return 1;   //递归头
        }else {
            return n * f(n-1);   //递归体
        }
    }

4.7 作业计算器

加减乘除循环接收用户交互

 public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("1:加法 2：剑法 3：惩罚 4：除法");
        System.out.println("请输入要执行的操作");
        while (scanner.hasNext()){
            int x = scanner.nextInt();
            System.out.println("请输入两个数");
            double a = scanner.nextDouble();
            double b = scanner.nextDouble();
            switch (x){
                case 1:
                    System.out.println(add(a,b));
                    break;
                case 2:
                    System.out.println(jian(a,b));
                    break;
                case 3:
                    System.out.println(cheng(a,b));
                    break;
                case 4:
                    System.out.println(chu(a,b));
                    break;
                default:
                    System.out.println("小猫咪不知道哦");
            }
            System.out.println("请输入要执行的操作");
        }
    }
    public static double add(double a,double b){
        return a+b;
    }
    public static double jian(double a,double b){
        return a-b;
    }
    public static double cheng(double a,double b){
        return a*b;
    }
    public static double chu(double a,double b){
        return a/b;
    }