package demo; import java.io.File; import java.util.Scanner; public class Test1 { public static void main(String[] args) { File file = getDirectory(); System.out.println(fileSize(file)); } // Determine whether it is a folder public static File getDirectory() { Scanner sc = new Scanner(System.in); System.out.print("Please enter the file path:"); while (true) { String path = sc.next(); File file = new File(path); if (!file.exists()) { System.out.print("File does not exist, please re-enter:"); } else if (file.isFile()) { System.out.print("You entered the file path,Please re-enter:"); } else { return file; } } } // Use recursion to determine folder size public static int fileSize(File file) { int size = 0; File[] files = file.listFiles(); for (File file1 : files) { if (file1.isFile()) { size += file1.length(); } else { size += fileSize(file1); } } return size; } }2. Receive a folder path from the keyboard and delete the folder
package demo; import java.io.File; import java.util.Scanner; public class Test2 { public static void main(String[] args) { File file = getDirectory(); deleteDirectory(file); if (file.exists()) { System.out.println("Delete failed"); } else { System.out.println("Delete successful"); } } // Determine whether it is a folder public static File getDirectory() { Scanner sc = new Scanner(System.in); System.out.print("Please enter the file path:"); while (true) { String path = sc.next(); File file = new File(path); if (!file.exists()) { System.out.print("File does not exist, please re-enter:"); } else if (file.isFile()) { System.out.print("You entered the file path,Please re-enter:"); } else { return file; } } } // Use recursion to delete folders public static void deleteDirectory(File file) { File[] files = file.listFiles(); for (File file1 : files) { if (file1.isFile()) { file1.delete(); } else { deleteDirectory(file1); } } // Delete files when there are no files in the folder file.delete(); } }3. Receive two folder paths from the keyboard, and copy one folder (including content) to the other
package demo; import java.io.BufferedInputStream; import java.io.BufferedOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.util.Scanner; public class Test3 { public static void main(String[] args) throws IOException { File src = getDirectory(); File dest = getDirectory(); if (src.equals(dest)) { System.out.println("The destination folder is a subfolder of the original folder"); } else { copyFile(src, dest); } } // Determine whether it is a folder public static File getDirectory() { Scanner sc = new Scanner(System.in); System.out.print("Please enter the file path:"); while (true) { String path = sc.next(); File file = new File(path); if (!file.exists()) { System.out.print("File does not exist, please re-enter:"); } else if (file.isFile()) { System.out.print("You entered the file path,Please re-enter:"); } else { return file; } } } // Using recursive copy folders public static void copyFile(File src, File dest) throws IOException { // First create the original folder in the destination folder File newFile = new File(dest, src.getName()); newFile.mkdir(); // Traverse files and folders in the original file File[] files = src.listFiles(); for (File file1 : files) { if (file1.isFile()) { BufferedInputStream bis = new BufferedInputStream(new FileInputStream(file1)); BufferedOutputStream bos = new BufferedOutputStream( new FileOutputStream(new File(newFile, file1.getName()))); int b; while ((b = bis.read()) != -1) { bos.write(b); } bis.close(); bos.close(); } else { copyFile(file1, newFile); } } } }4. Receive a folder path from the keyboard, and print all the files in the folder and the folder name by level
package demo; import java.io.File; import java.io.IOException; import java.util.Scanner; public class Test4 { public static void main(String[] args) throws IOException { File file = getDirectory(); tierPrint(file, 0); } // Determine whether it is a folder public static File getDirectory() { Scanner sc = new Scanner(System.in); System.out.print("Please enter the file path:"); while (true) { String path = sc.next(); File file = new File(path); if (!file.exists()) { System.out.print("File does not exist, please re-enter:"); } else if (file.isFile()) { System.out.print("You entered the file path,Please re-enter:"); } else { return file; } } } // Print hierarchically using recursion public static void tierPrint(File file, int lev) throws IOException { File[] files = file.listFiles(); for (File file1 : files) { for (int i = 0; i < lev; i++) { System.out.print("\t"); } System.out.println(file1.getPath()); if (file1.isDirectory()) { tierPrint(file1, lev + 1); } } } }5. Suppose that a pair of new born rabbits can grow into a big one in one month, and then a pair of small rabbits can be born in another month. After that, a pair of small rabbits will be born every month, and there will be no death within one year,
Q: how many pairs of new born rabbits can be bred in one year?
Rule: 1 1 2 3 5 8 13 21
package demo; import java.util.Scanner; public class Test5 { public static void main(String[] args) { // Rule: 1 1 2 3 5 8 13 21 Scanner sc = new Scanner(System.in); System.out.print("Please enter the number of days:"); int day = sc.nextInt(); System.out.println(recursion(day)); // System.out.println(array(day)); } // Use recursion for calculation public static int recursion(int day) { if (day == 1 || day == 2) { return 1; } else { return recursion(day - 2) + recursion(day - 1); } } // Calculated by array public static int array(int day) { int[] is = new int[day]; is[0] = 1; is[1] = 1; for (int i = 2; i < is.length; i++) { is[i] = is[i - 2] + is[i - 1]; } return is[is.length - 1]; } }6. Joseph Ring N people form a circle, and report from the first one. Every third person will be killed, and the last one will be left, and the rest will be killed.
package demo; import java.util.ArrayList; public class Test6 { public static void main(String[] args) { System.out.println(getLucklyNum(8));// 7 } public static int getLucklyNum(int num) { ArrayList<Integer> list = new ArrayList<Integer>(); for (int i = 1; i <= num; i++) { list.add(i); } // count int count = 1; for (int i = 0; list.size() != 1; i++) { // If the subscript exceeds the maximum subscript, it is equivalent to another call from a person if (i == list.size()) { i = 0; } // Delete one for every three people if (count % 3 == 0) { list.remove(i); i--; } count++; } // The last one back return list.get(0); } }
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