Method recursion and file example in Java

1, there are a pair of rabbits, from the 3rd month after birth every month, a pair of rabbits, the rabbit long to the third month after the birth of a pair of rabbits, if the rabbit is not dead, ask the 20th month of the rabbit logarithm is how much? (No Death rabbit)
(1) Array mode

package 递归.作业;public class TuziArray {    public static void main(String[] args) {           //定义数组         int arr[] = new int[100];           int m=20;               arr[1] = 1;//前两个月兔子数量为1只           arr[2] = 1;           arr[3] = 2;                    for(int i=1;i<=m;i++){              if(i>=3){                    //规律为：斐波那契数列规律                  arr[i] = arr[i-1] +arr[i-2];               }           }            System.out.println("第20个月的兔子对数为："+arr[20]);      }}

(2) Recursive method

package 递归.作业;public class Tuzi {    public static void main(String[] args) {        // 調用rabbit()方法        int rabbit = rabbit(20);        System.out.println("第20个月的兔子对数为： " + rabbit);    }    public static int rabbit(int mouth) {        // 前兩個月只有一對兔子        if (mouth == 1 || mouth == 2) {            return 1;        }        // 上一个月的兔子数        int rabbit1 = rabbit(mouth - 1);        // 上一个月的前一个月兔子数        int rabbit2 = rabbit(mouth - 2);        // 斐波那契額函數        return rabbit1 + rabbit2;    }}

2. Requirements: Recursive removal of contents with content
Suppose there is a demo folder under the project path with some folders and some files, please use recursive thinking to implement.

package 递归.作业;import java.io.File;public class FileDiGui2 {    public static void main(String[] args) {            // 封装File对象          File demo = new File("demo");          // 调用递归删除方法          deleteFile(demo);      }         // 方法递归:删除      public static void deleteFile(File demo) {          // 获取该文件夹下的文件或文件夹路径名数组          File[] demoFile = demo.listFiles();          // 非空判断          if (demoFile != null) {               // 遍历demofile数组对象               for (File file : demoFile) {                     // 判断file里面的对象是不是标准文件,如果是则递归调用该方法进行继续判断                     if (file.isFile()) {                         deleteFile(file);                     } else {// 否则是一个文件夹,执行输出文件名,并删除                          System.out.println(file.getName() + "---" + file.delete());                     }                }           }      }   }

3. Requirements: Please put the absolute path of all Java end files in the E:\JavaSE directory to the output in the console.

package File类.作业;import java.io.File;public class OutputE {    public static void main(String[] args) {          // 创建文件对象  ,指向E:\\JavaSE        File file = new File("E:\\JavaSE");          // 获取file对象内的文件/文件夹路径名数组          File[] files = file.listFiles();          // 遍历files数组        for (File f : files) {              // 获取f对象文件名,判断是否以".java"结尾,如果是输出路径名              if (f.getName().endsWith(".java"))              System.out.println(f);          }     }  }

Method recursion and file example in Java