Java中的IO處理

創建文件夾：file.mkdir()

CreatDirectoryDemo.java

1. package com.tianjf;
3. import java.io.File;
5. public class CreatDirectoryDemo {
6. public static void main(String[] args) {
7. String directoryName = "D:" + File.separator + "hello";
8. File file = new File(directoryName);
9. file.mkdir();
10. }
11. }

創建文件：file.createNewFile()

1. package com.tianjf;
3. import java.io.File;
4. import java.io.IOException;
6. public class CreatFileDemo {
7. public static void main(String[] args) {
8. String fileName = "D:" + File.separator + "hello.txt";
9. File file = new File(fileName);
10. try {
11. file.createNewFile();
12. } catch (IOException e) {
13. e.printStackTrace();
14. }
15. }
16. }

判斷指定路徑是文件夾還是文件：file.isDirectory() / file.isFile()

IsDirectoryOrFileDemo.java

1. package com.tianjf;
3. import java.io.File;
5. public class IsDirectoryOrFileDemo {
6. public static void main(String[] args) {
7. String directoryName = "D:" + File.separator + "hello";
8. File file = new File(directoryName);
9. if (file.isDirectory()) {
10. System.out.println("是一個文件夾！");
11. } else {
12. System.out.println("不是一個文件夾！");
13. }
15. String fileName = "D:" + File.separator + "hello.txt";
16. file = new File(fileName);
17. if (file.isFile()) {
18. System.out.println("是一個文件！");
19. } else {
20. System.out.println("不是一個文件！");
21. }
22. }
23. }

刪除文件：file.delete()

DeleteFileDemo.java

1. package com.tianjf;
3. import java.io.File;
5. public class DeleteFileDemo {
6. public static void main(String[] args) {
7. String fileName = "D:" + File.separator + "hello.txt";
8. File file = new File(fileName);
9. if (file.exists()) {
10. file.delete();
11. } else {
12. System.out.println("文件不存在");
13. }
14. }
15. }

列出所有文件夾名和所有文件名：file.list() / 列出所有文件夾路徑和所有文件路徑：file.listFiles()

ListFilesDemo.java

1. package com.tianjf;
3. import java.io.File;
5. public class ListFilesDemo {
6. public static void main(String[] args) {
7. String directoryName = "D:" + File.separator;
8. File file = new File(directoryName);
10. // 列出所有文件夾名和所有文件名
11. String[] arrStr = file.list();
12. for (int i = 0; i < arrStr.length; i++) {
13. System.out.println(arrStr[i]);
14. }
16. // 列出所有文件夾路徑和所有文件路徑
17. System.out.println("---------------------------------------");
18. File[] arrFile = file.listFiles();
19. for (int i = 0; i < arrFile.length; i++) {
20. System.out.println(arrFile[i]);
21. }
23. // 列出所有文件夾路徑和所有文件路徑
24. System.out.println("---------------------------------------");
25. File[] arrFileWithFilter = file.listFiles(new FilenameFilter() {// 內部類
26. @Override
27. public boolean accept(File f1, String name) {
28. return name.endsWith(".txt");
29. }
30. });
31. for (int i = 0; i < arrFileWithFilter.length; i++) {
32. System.out.println(arrFileWithFilter[i]);
33. }
34. }
35. }

寫入字節流：FileOutputStream

FileOutputStreamDemo.java

1. package com.tianjf;
3. import java.io.File;
4. import java.io.FileOutputStream;
5. import java.io.IOException;
6. import java.io.OutputStream;
8. public class FileOutputStreamDemo {
9. public static void main(String[] args) throws IOException {
10. /* 將一個字符串作為一個整體寫入文件 */
11. String fileName01 = "D:" + File.separator + "hello01.txt";
12. File file01 = new File(fileName01);
13. String str01 = "你好";
14. byte[] bytes01 = str01.getBytes();
15. OutputStream out01 = new FileOutputStream(file01);
16. out01.write(bytes01);
17. // 刷新緩存，寫文件，最好加上這樣的一句話
18. out01.flush();
19. out01.close();
21. /* 將一個字符串一個字節一個字節的寫入文件 */
22. String fileName02 = "D:" + File.separator + "hello02.txt";
23. File file02 = new File(fileName02);
24. String str02 = "你好";
25. byte[] bytes02 = str02.getBytes();
26. OutputStream out02 = new FileOutputStream(file02);
27. for (int i = 0; i < bytes02.length; i++) {
28. out02.write(bytes02[i]);
29. }
30. out02.flush();
31. out02.close();
33. /* 追加新內容到文件中 */
34. String str03 = "追加的內容";
35. byte[] bytes03 = str03.getBytes();
36. OutputStream out03 = new FileOutputStream(file02, true);
37. for (int i = 0; i < bytes03.length; i++) {
38. out03.write(bytes03[i]);
39. }
40. out03.flush();
41. out03.close();
42. }
43. }