Java多種寫文件方式

時間 2019-11-07

標籤 java 多種文件方式欄目 Java 简体版

原文原文鏈接

寫文件在開發小工具時經常使用到，好比爬取某些網站的信息，數據量不是很大，保存到本地便可。固然若是會一些額外的技能，好比多線程，網絡之類的，小工具會更加有意思。java

這裏看下Java不一樣的寫文件方式：數組

BufferedWriter
PrintWriter
FileOutputStream
DataOutputStream
RandomAccessFile
FileChannel
Files

BufferedWriter

把類中定義的方法信息，寫入文件bash

static String fileName = "/Users/aihe/tmp/writeFileDemo.txt";
	static void writeFileWithBufferedWriter() throws IOException {
        Method[] methods = WriteFileDemo.class.getDeclaredMethods();
        String str = Arrays.toString(methods);
        BufferedWriter writer = new BufferedWriter(new FileWriter(fileName));
        writer.write(str);
        writer.close();
    }
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追加信息到已經存在的文件：網絡

static void appendFileWithBufferedWriter() throws IOException {
    	// FileWriter的第二個參數表明是否追加
        BufferedWriter writer = new BufferedWriter(new FileWriter(fileName,true));
        writer.append("追加信息");
        writer.close();
    }
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PrintWriter

PrintWriter能夠輸出格式化的信息到文件中。多線程

static void writingFileWithPrintWriter() throws IOException {
        Method[] methods = WriteFileDemo.class.getDeclaredMethods();
        String str = Arrays.toString(methods);
		// 能夠使用FileWriter,BufferedWriter
        FileWriter fileWriter = new FileWriter(fileName);
        PrintWriter printWriter = new PrintWriter(fileWriter);
        printWriter.printf("當前類的方法信息： %s \n方法的個數：%d \n", str, methods.length);
        printWriter.close();
    }
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FileOutputStream

用來寫入二進制數據到文件中，須要將String轉換爲bytes。app

static void writingFileWithFileOutputStream() throws IOException {
        Method[] methods = WriteFileDemo.class.getDeclaredMethods();
        String str = Arrays.toString(methods);

        FileOutputStream outputStream = new FileOutputStream(fileName);
        // 須要將String轉換爲bytes
        byte[] strToBytes = str.getBytes();
        outputStream.write(strToBytes);

        outputStream.close();
    }
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DataOutputStream

寫法如上dom

static void writingFileWithDataOutputStream()
            throws IOException {
        Method[] methods = WriteFileDemo.class.getDeclaredMethods();
        String str = Arrays.toString(methods);

        FileOutputStream fos = new FileOutputStream(fileName);
        DataOutputStream outStream = new DataOutputStream(new BufferedOutputStream(fos));
        outStream.writeUTF(str);
        outStream.close();

        // verify the results
        String result;
        FileInputStream fis = new FileInputStream(fileName);
        DataInputStream reader = new DataInputStream(fis);
        result = reader.readUTF();
        reader.close();

        System.out.println(result.equals(str));
    }
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RandomAccessFile

想要寫入或者編輯一個已經存在的文件，而不是寫入一個全新的文件或者單純的追加，那麼咱們能夠使用RandomAccessFile。這個類能夠讓咱們寫入特定的位置，以下：工具

寫入中文的時候使用writeUTF方法，否則可能會亂碼網站

static void writeToPositionWithRAF(String filename, long position)
            throws IOException {
        RandomAccessFile writer = new RandomAccessFile(filename, "rw");
        writer.seek(position);
        //寫入中文的時候防止亂碼
        writer.writeUTF("新內容");
        writer.close();
    }
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FileChannel

在處理大文件的時候，FileChannel會比標準的io更快。ui

static void writeWithFileChannel() throws IOException {
    RandomAccessFile stream = new RandomAccessFile(fileName, "rw");
    FileChannel channel = stream.getChannel();

    String value = WriteFileDemo.class.getSimpleName();
    byte[] strBytes = value.getBytes();
    ByteBuffer buffer = ByteBuffer.allocate(strBytes.length);
    buffer.put(strBytes);
    buffer.flip();
    channel.write(buffer);

    stream.close();
    channel.close();

}
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Files

Files是Java7引入的工具類，經過它，咱們能夠建立，移動，刪除，複製文件。目錄也是一種特殊的文件，對目錄也適用。固然也能夠用於讀寫文件

static void writeWithFiles()
            throws IOException {
        String str = "Hello";

        Path path = Paths.get(fileName);
        byte[] strToBytes = str.getBytes();

        Files.write(path, strToBytes);

        String read = Files.readAllLines(path).get(0);

        System.out.println(str.equals(read));
    }
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