Java File类文件管理及IO读写、复制操作

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

?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
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 exception
            e.printStackTrace();
        }
    } else {
        System.out.println("文件已存在");
    }
}

创建文件夹

?
1
2
3
4
5
6
7
8
9
10
11
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：

?
1
2
3
4
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

?
1
2
3
4
5
6
7
8
9
10
11
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写入文件

?
1
2
3
4
5
6
7
8
9
10
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：

?
1
2
3
4
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

?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
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： "+data);
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

用FileInputStream读取文件

?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
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： "+data);
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

用BufferedReader读取文件

?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
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(" ");
        }
    } catch (Exception e) {
        // TODO: handle exception
        e.printStackTrace();
    }
    System.out.println(fileName+"中按BufferedReader读取的文件内容是： "+buffer.toString());
}

应用：
?
1
2
3
4
5
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

?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
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

?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
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

?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
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();
    }
}

应用：

?
1
2
3
4
5
6
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");
}
转自：http://www.open-open.com/lib/view/open1379940752711.html
【推广】 免费学中医，健康全家人
原文地址：https://www.cnblogs.com/91loveme/p/4063181.html