java io 相关常用操作详解

File类的总结：

1.文件和文件夹的创建

2.文件的读取

3.文件的写入

4.文件的复制（字符流、字节流、处理流）

5.以图片地址下载图片

文件和文件夹

相关函数

 (boolean) mkdir() 创建此抽象路径名指定的目录
 (boolean) mkdirs() 创建此抽象路径名指定的目录，包括所有必需但不存在的父目录。
 (boolean) delete() 删除此抽象路径名表示的文件或目录
 (boolean) createNewFile() 当不存在此路径名指定名称的文件时，创建一个新的空文件。
 

创建文件

public static void NewFile(String pathString) {File file = new File(pathString);if (!file.exists()) {try {if (file.createNewFile()) {System.out.println("文件创建成功");}} catch (Exception e) {// TODO: handle exceptione.printStackTrace();}} else {System.out.println("文件已存在");}}

创建文件夹

public static void NewFileBox(String pathString) {File file2 = new File(pathString);if (!file2.exists()) {if (file2.mkdirs()) {System.out.println("文件夹成功");}} else {System.out.println("文件夹存在");file2.delete();//销毁文件}}

应用：

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

Writer写入文件

用FileWriter写入文件

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 exceptione.printStackTrace();}}

用BufferedWriter写入文件

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();}}

应用：

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

Reader读取文件

用FileReader读取文件

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读取的文件内容是：\n"+data);} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}

用FileInputStream读取文件

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读取的文件内容是：\n"+data);} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}

用BufferedReader读取文件

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 exceptione.printStackTrace();}System.out.println(fileName+"中按BufferedReader读取的文件内容是：\n"+buffer.toString());}

应用：

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

文件的复制操作

字符流复制

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);}}

字节流复制

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);}}

处理流复制

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 exceptione.printStackTrace();}}

应用：

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");}