Java學習第六課 JAVA 文件操作

平常經常使用JAVA對文件進行讀寫等操作，這裏彙總一下常用的文件操作。

1、創建文件

public static boolean createFile(String filePath){
    boolean result = false;
    File file = new File(filePath);
    if(!file.exists()){
        try {
            result = file.createNewFile();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    return result;
}

2、創建文件夾

public static boolean createDirectory(String directory){
    boolean result = false;
    File file = new File(directory);
    if(!file.exists()){
        result = file.mkdirs();
    }

    return result;
}

3、刪除文件

public static boolean deleteFile(String filePath){
    boolean result = false;
    File file = new File(filePath);
    if(file.exists() && file.isFile()){
        result = file.delete();
    }

    return result;
}

4、刪除文件夾

遞歸刪除文件夾下面的子文件和文件夾

public static void deleteDirectory(String filePath){
    File file = new File(filePath);
    if(!file.exists()){
        return;
    }

    if(file.isFile()){
        file.delete();
    }else if(file.isDirectory()){
        File[] files = file.listFiles();
        for (File myfile : files) {
            deleteDirectory(filePath + "/" + myfile.getName());
        }

        file.delete();
    }
}

5、讀文件

（1）以字節爲單位讀取文件，常用於讀二進制文件，如圖片、聲音、影像等文件

public static String readFileByBytes(String filePath){
    File file = new File(filePath);
    if(!file.exists() || !file.isFile()){
        return null;
    }

    StringBuffer content = new StringBuffer();

    try {
        byte[] temp = new byte[1024];
        FileInputStream fileInputStream = new FileInputStream(file);
        while(fileInputStream.read(temp) != -1){
            content.append(new String(temp));
            temp = new byte[1024];
        }

        fileInputStream.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    return content.toString();
}

 （2）以字符爲單位讀取文件，常用於讀文本，數字等類型的文件，支持讀取中文

public static String readFileByChars(String filePath){
    File file = new File(filePath);
    if(!file.exists() || !file.isFile()){
        return null;
    }

    StringBuffer content = new StringBuffer();
    try {
        char[] temp = new char[1024];
        FileInputStream fileInputStream = new FileInputStream(file);
        InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream, "GBK");
        while(inputStreamReader.read(temp) != -1){
            content.append(new String(temp));
            temp = new char[1024];
        }

        fileInputStream.close();
        inputStreamReader.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    return content.toString();
}

（3）以行爲單位讀取文件，常用於讀面向行的格式化文件

public static List<String> readFileByLines(String filePath){
    File file = new File(filePath);
    if(!file.exists() || !file.isFile()){
        return null;
    }

    List<String> content = new ArrayList<String>();
    try {
        FileInputStream fileInputStream = new FileInputStream(file);
        InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream, "GBK");
        BufferedReader reader = new BufferedReader(inputStreamReader);
        String lineContent = "";
        while ((lineContent = reader.readLine()) != null) {
            content.add(lineContent);
            System.out.println(lineContent);
        }

        fileInputStream.close();
        inputStreamReader.close();
        reader.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    return content;
}

6、寫文件

字符串寫入文件的幾個類中，FileWriter效率最高，BufferedOutputStream次之，FileOutputStream最差。

（1）通過FileOutputStream寫入文件

public static void writeFileByFileOutputStream(String filePath, String content) throws IOException{
    File file = new File(filePath);
    synchronized (file) {
        FileOutputStream fos = new FileOutputStream(filePath);
        fos.write(content.getBytes("GBK"));
        fos.close();
    }
}

（2）通過BufferedOutputStream寫入文件

public static void writeFileByBufferedOutputStream(String filePath, String content) throws IOException{
    File file = new File(filePath);
    synchronized (file) {
        BufferedOutputStream fos = new BufferedOutputStream(new FileOutputStream(filePath));
        fos.write(content.getBytes("GBK"));
        fos.flush();
        fos.close();
    }
}

（3）通過FileWriter將字符串寫入文件

public static void writeFileByFileWriter(String filePath, String content) throws IOException{
        File file = new File(filePath);
        synchronized (file) {
            FileWriter fw = new FileWriter(filePath);
            fw.write(content);
            fw.close();
        }
    }

 本文轉載自：http://blog.csdn.net/brushli/article/details/12356695