File類的總結：

1.檔案和資料夾的建立

2.檔案的讀取

3.檔案的寫入

4.檔案的複製（字元流、位元組流、處理流）

5.以圖片地址下載圖片

檔案和資料夾

相關函式

建立檔案

	public static void NewFile(String pathString) {
		File file = new File(pathString);
		if (!file.exists()) {
			try {
				if (file.createNewFile()) {
					System.out.println("檔案建立成功");
				}
			} catch (Exception e) {
				// TODO: handle exception
				e.printStackTrace();
			}
		} else {
			System.out.println("檔案已存在");
		}
	}
 

建立資料夾

	public static void NewFileBox(String pathString) {
		File file2 = new File(pathString);
		if (!file2.exists()) {
			if (file2.mkdirs()) {
				System.out.println("資料夾成功");
			}
		} else {
			System.out.println("資料夾存在");
			file2.delete();//銷燬檔案
		}
	}

應用：

	public static void main(String[] args) {
		NewFile("test/file.txt");
		NewFileBox("test/a/a/a/a");
	}
 

Writer寫入檔案

用FileWriter寫入檔案

	public  static void ForFileWriter(String string,String fileName) {
		File file = new File(fileName);
		try {
			FileWriter fWriter = new FileWriter(file);
			fWriter.write(string);
			fWriter.close();
		} catch (Exception e) {
			// TODO: handle exception
			e.printStackTrace();
		}
	}
 

用BufferedWriter寫入檔案

	public static void ForBufferedWriter(String string,String desFile) {
		BufferedWriter bWriter = null;
		try {
			bWriter = new BufferedWriter(new FileWriter(new File(desFile)));
			bWriter.write(string.toString());
			bWriter.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

應用：

	public static void main(String[] args) {
		ForFileWriter("用FileWriter寫入檔案", "test/writer1.txt");
		ForBufferedWriter("用BufferedWriter寫入檔案", "test/writer2.txt");
	}

Reader讀取檔案

用FileReader讀取檔案

	public static void testReadByReader(String fileName){
		File file = new File(fileName);
		FileReader fis = null;
		try {
			fis =  new FileReader(file);
			char[] arr = new char[1024 * 1000 * 6];
			int len = fis.read(arr);
			String data = new String(arr, 0, len);
			fis.close();
			System.out.println(fileName+"中按FileReader讀取的檔案內容是：\n"+data);
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

用FileInputStream讀取檔案

	public static void testReadByInputStream(String fileName){
		File file = new File(fileName);
		FileInputStream fis = null;
		try {
			fis =  new FileInputStream(file);
			byte[] arr = new byte[1024 * 1000 * 6];
			int len = fis.read(arr);
			String data = new String(arr, 0, len);
			fis.close();
			System.out.println(fileName+"中按FileInputStream讀取的檔案內容是：\n"+data);
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

用BufferedReader讀取檔案

	public static void testReadByBufferedReader(String fileName) {
		BufferedReader bReader = null;
		String line = null;
		StringBuffer buffer = new StringBuffer();
		try {
			bReader =new BufferedReader(new FileReader(new File(fileName)));
			while ((line = bReader.readLine())!=null) {
				buffer.append(line).append("\n");
			}
		} catch (Exception e) {
			// TODO: handle exception
			e.printStackTrace();
		}
		System.out.println(fileName+"中按BufferedReader讀取的檔案內容是：\n"+buffer.toString());
	}

	public static void main(String[] args) {
		testReadByInputStream("res/我.txt");
		testReadByReader("res/我.txt");
		testReadByBufferedReader("res/我.txt");
	}

檔案的複製操作

字元流複製

	public static void FileCopy1(String readfile,String writeFile) {
		try {
			FileReader input = new FileReader(readfile);
			FileWriter output = new FileWriter(writeFile);
			int read = input.read();		
			while ( read != -1 ) {
				output.write(read);	
				read = input.read();
			}			
			input.close();
			output.close();
		} catch (IOException e) {
			System.out.println(e);
		}
	}

位元組流複製

	public static void FileCopy2(String readfile,String writeFile) {
		try {
			FileInputStream input = new FileInputStream(readfile);
			FileOutputStream output = new FileOutputStream(writeFile);
			int read = input.read();		
			while ( read != -1 ) {
				output.write(read);	
				read = input.read();
			}			
			input.close();
			output.close();
		} catch (IOException e) {
			System.out.println(e);
		}
	}

處理流複製

	public static void FileCopy3(String readfile,String writeFile) {
		BufferedReader bReader = null;
		BufferedWriter bWriter = null;
		String line = null; 
		try {
			bReader = new BufferedReader(new FileReader(new File(readfile)));
			bWriter = new BufferedWriter(new FileWriter(new File(writeFile)));
			while ((line = bReader.readLine())!=null) {
				bWriter.write(line);
				bWriter.newLine();
			}
			bWriter.close();
			bReader.close();
		} catch (Exception e) {
			// TODO: handle exception
			e.printStackTrace();
		}
	}

應用：

	public static void main(String[] args) {
		FileCopy1("res/我.txt", "test/1.txt");
		FileCopy2("res/我.txt", "test/2.txt");
		FileCopy3("res/我.txt", "test/3.txt");
		FileCopy2("res/me.jpg", "test/33.jpg");
	}

原始碼下載：