Java File 文件操作

java.io包里的类：

• InputStream/OutputStream ： 以字节为单位读写文件内容，一次读/写一个字节，常用于读二进制文件，如图片、音频、视频等文件

• FileInputStream/FileOutputStream : 以字节为单位读写文件内容，一次读写多个字节

• Reader/Writer : 以字符为单位，一次读写一个字符

• BufferedReader/BufferedWriter : 以行为单位，一次读写一行，以换行符为结束标志

java.nio (new i/o)（jdk 1.4加入）
特点：非阻塞

创建方法

1. boolean createNewFile() 不存在返回true 存在返回false
2. boolean mkdir() 创建目录
3. boolean mkdirs() 创建多级目录

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删除方法

1. boolean delete()
2. boolean deleteOnExit() 文件使用完成后删除

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判断方法

1. boolean canExecute()判断文件是否可执行
2. boolean canRead()判断文件是否可读
3. boolean canWrite() 判断文件是否可写
4. boolean exists() 判断文件是否存在
5. boolean isDirectory() 判断是否是一个目录
6. boolean isFile() 判断是否是一个文件
7. boolean isHidden()8.boolean isAbsolute()判断是否是绝对路径 文件不存在也能判断

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获取方法

1. String getName() 返回文件名
2. String getPath()
3. String getAbsolutePath()
4. String getParent()//如果没有父目录返回null
5. long lastModified()//获取最后一次修改的时间
6. long length()
7. boolean renameTo(File f)
8. File[] liseRoots()//获取机器盘符
9. String[] list()
10. String[] list(FilenameFilter filter)

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具体文件操作代码：

1. 创建文件/文件夹 :

//创建文件夹
    public static void createFolder(String path){
        File file = new File(path);
        file.mkdirs();
    }
    
    //创建文件
    public static boolean createFile(String fileName){
        File file = new File(fileName);
        System.out.println(file.getAbsolutePath());
        boolean isSucess = false;
        try {
            isSucess = file.createNewFile();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return isSucess;
    }

2. 写文件：

//写入文件
    public static void writeFile(String fileName){
        File file = new File(fileName);
        BufferedWriter bWriter = null;
        try {
            FileWriter writer = new FileWriter(file);
            bWriter = new BufferedWriter(writer);
            bWriter.write("hello ");
            bWriter.newLine();
            bWriter.write('a');
            bWriter.write(27);
            bWriter.write("world");
            
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            if (bWriter != null) {
                try {
                    bWriter.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

3. 读文件：

//读取文件
    public static void readFile(String fileName){
        File file = new File(fileName);
        BufferedReader bReader = null;
        try {
            FileReader reader = new FileReader(file);
            bReader = new BufferedReader(reader);
            String line = bReader.readLine();
            while(line != null){
                System.out.println(line);
                line = bReader.readLine();
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }catch(IOException e){
            e.printStackTrace();
        }finally {
            try {
                if (bReader != null) {
                    bReader.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

4. 列出当前目录下所有文件：

//列出当前目录下的所有文件
    public static void listFile(String folderPath){
        File file = new File(folderPath);
        for(String fileName : file.list()){
            System.out.println("fileName : "+ fileName);
        }
    }

4. 删除文件：

//删除文件
    public static void delFile(String folderPath){
        File file = new File(folderPath);
        System.out.println(folderPath);
        file.delete();
    }

6. 拷贝文件：

7. 方法一：

public static void copyFile(String oldPath, String newPath){
        File oldFile = new File(oldPath);
        File newFile = new File(newPath);
        BufferedReader bReader = null;
        BufferedWriter bWriter = null;
        try {
            FileReader fr = new FileReader(oldFile);
            bReader = new BufferedReader(fr);
            String all = "";
            String line = bReader.readLine();
            System.out.println("拷贝中。。。请稍候");
            while(line != null){
                all += line;
                line = bReader.readLine();
            }
            FileWriter fw = new FileWriter(newFile);
            bWriter = new BufferedWriter(fw);
            bWriter.write(all);
            System.out.println("完成！");
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }catch(IOException e){
            e.printStackTrace();
        }finally {
            try {
                bReader.close();
                bWriter.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

2. 方法二：

public static void copyFile2(File source, File dest) throws IOException {
        InputStream input = null;
        OutputStream output = null;
        try {
            input = new FileInputStream(source);
            output = new FileOutputStream(dest);
            byte[] buf = new byte[1024];
            int bytesRead;
            System.out.println("拷贝中。。。请稍候");
            while ((bytesRead = input.read(buf)) > 0) {
                output.write(buf, 0, bytesRead);
            }
            System.out.println("完成！");
        } finally {
            input.close();
            output.close();
        }
    }

3. 方法三：

public static void copyFiles(File source, File dest){
        try {
            System.out.println("拷贝中。。。请稍候");
            Files.copy(source.toPath(), dest.toPath());
            System.out.println("完成！");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }