J2SE 8的输入输出--读取/写入文本文件和读取/写入二进制数据

读取/写入文本文件

// 1. 文本输入
// (1) 短小文本直接转入字符串
String string = new String(Files.readAllBytes(Paths.get("E:\\111.txt")), StandardCharsets.UTF_8);
System.out.println(string);
System.out.println();

// (2) 按行读取Files.readAllLines() -> List<String>
List<String> strings = Files.readAllLines(Paths.get("E:\\111.txt"), StandardCharsets.UTF_8);
System.out.println(strings);
System.out.println();

// (3) 文件太大可以转换为Files.lines() -> Stream<String>
Stream<String> lines = Files.lines(Paths.get("E:\\111.txt"), StandardCharsets.UTF_8);
lines.forEach(n -> System.out.println(n));
System.out.println();

// (4) 常规方法 BufferedReader.readLine()
String line = null;
String total = "";
try (BufferedReader bufferedReader = new BufferedReader(
        new InputStreamReader(new FileInputStream("E:\\111.txt"), StandardCharsets.UTF_8))) {
    while ((line = bufferedReader.readLine()) != null) {
        total = total + line + File.separator;
    }
}
System.out.println(total);
System.out.println();

// (5) 常规方法->流 BufferedReader.lines()
try (BufferedReader bufferedReader = new BufferedReader(
        new InputStreamReader(new FileInputStream("E:\\111.txt"), StandardCharsets.UTF_8))) {
    Stream<String> lines2 = bufferedReader.lines();
    lines2.forEach(n -> System.out.println(n));
}

// 2. 文本输出
// (1)常规输出 BufferedWriter->OutputStreamWriter->FileOutputStream
try (BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("E:\\222.txt")))) {
    bw.write("文本输出");
    bw.write("文本输出");
    bw.write("文本输出");
}

// (2) 使用 FileWriter
try (FileWriter fileWriter = new FileWriter("E:\\222.txt")) {
    fileWriter.write("文本输出");
    fileWriter.write("文本输出");
    fileWriter.write("文本输出");
}

// (3) 使用 PrintWriter println()可以自动换行
try (PrintWriter printWriter = new PrintWriter("E:\\222.txt")) {
    printWriter.write("文本输出");
    printWriter.write("文本输出");
    printWriter.write("文本输出");

    printWriter.println("文本输出");
    printWriter.println("文本输出");
    printWriter.println("文本输出");

}

// 3. 从控制台读入
 try(BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in))){
     String tempLine = null;
    
     while((tempLine=bufferedReader.readLine())!=null &&  !tempLine.contains("exit")){
         System.out.println(tempLine);
     }
 }

// 4. 通过System.out传入文本
PrintStream defaultOut = System.out;
System.setOut(new PrintStream("E:\\333.txt"));
System.out.println("文本输出");
System.setOut(defaultOut);

// 5. 字符集
// (1) 默认字符集
System.out.println(Charset.defaultCharset());

// (2) 可用字符集
// SortedMap<String, Charset> availableCharsets =
// Charset.availableCharsets();
// availableCharsets.entrySet().forEach(n->System.out.println(n.getKey()+"  "+n.getValue()));

// (3) 指定字符集
Charset utf_8 = StandardCharsets.UTF_8;
utf_8 = Charset.forName("UTF-8");	

读取/写入二进制文件

// 6.写入二进制文件
try (DataOutputStream dataOutputStream = new DataOutputStream(new FileOutputStream("E:\\111.data"))) {
    dataOutputStream.writeChars("二进制文本");
}
System.out.println();

// 7.读取二进制文件
try (DataInputStream dataInputStream = new DataInputStream(new FileInputStream("E:\\111.data"))) {
    //available() 在不阻塞的情况下，可以获取的字节数
    while (0 != dataInputStream.available()) {
        System.out.println(dataInputStream.readChar());
    }
}

随机文件访问


// 8. 随机文件访问
// (1) 二进制写入文件
try (DataOutputStream dataOutputStream = new DataOutputStream(new FileOutputStream("E:\\222.data"))) {
	writeFixedString("空白处", 20, dataOutputStream);
	writeFixedString("随机文件访问1", 30, dataOutputStream);
	writeFixedString("随机文件访问2", 40, dataOutputStream);
	dataOutputStream.writeDouble(88.88);
	dataOutputStream.writeInt(88);
}

// (2) 二进制读取文件
try (RandomAccessFile randomAccessFile = new RandomAccessFile("E:\\222.data", "r")) {
	System.out.println(randomAccessFile.length());

	// 中文占两个字节
	//seek() 离开始跳出的字节数
	randomAccessFile.seek(20 * 2);

	//getFilePointer()  当前位置
	System.out.println(randomAccessFile.getFilePointer());
	System.out.println("readFixedString:" + readFixedString(30, randomAccessFile));
	System.out.println("readFixedString:" + readFixedString(40, randomAccessFile));
	System.out.println(randomAccessFile.readDouble());
	System.out.println(randomAccessFile.readInt());

}

// (3) byte写入文件
try (RandomAccessFile randomAccessFile = new RandomAccessFile("E:\\333.data", "rw")) {
	// 不能使用writeBytes(), writeBytes(b, 0, len) len是字符串的length;
	// 而write()是bytes的length
	// randomAccessFile.writeBytes(s);

	randomAccessFile.write("随机文件访问2".getBytes());
	randomAccessFile.write("随机文件访问sss3".getBytes());

}

// (4) byte读取文件
try (RandomAccessFile randomAccessFile = new RandomAccessFile("E:\\333.data", "rw")) {
	int x = "随机文件访问2".getBytes().length;
	byte[] b = new byte[x];
	System.out.println(new String(b));

	int y = "随机文件访问sss3".getBytes().length;
	b = new byte[y];
	randomAccessFile.read(b);

	System.out.println(new String(b));

	// 从指定位置读取文件的功能
	b = new byte[1024];
	int hasRead = 0;
	while ((hasRead = randomAccessFile.read(b)) > 0) {		//只要能够读出来,就一直读
		System.out.print(new String(b, 0, hasRead));
	}
}

// (5)在文档末尾加字符
try (RandomAccessFile randomAccessFile = new RandomAccessFile("E:\\111.txt", "rw")) {
	//跳至文件末尾
	randomAccessFile.seek(randomAccessFile.length());

	randomAccessFile.writeBytes("The appended string");
}
System.out.println();

操作Zip文档

// 9. 操作Zip文档
//(1) 读取zip文档	ZipInputStream-->getNextEntry()		ZipFile-->getInputStream()
try(InputStream in = new FileInputStream("E:\\111.zip");
		ZipInputStream zipInputStream = new ZipInputStream(in);
		ZipFile zipFile = new ZipFile("E:\\111.zip");){
	ZipEntry entry = null;

	while((entry = zipInputStream.getNextEntry()) != null){
		try(InputStream inputStream = zipFile.getInputStream(entry);
				InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
				BufferedReader br = new BufferedReader(inputStreamReader);){
			System.out.println("ZipEntry	"+entry.getName());
			br.lines().forEach(n->System.out.println(n));
		}

		zipInputStream.closeEntry();
	}
}

//(2) 写入zip文档	ZipOutputStream-->putNextEntry
try(OutputStream outputStream= new FileOutputStream("E:\\222.zip");
		ZipOutputStream zipOutputStream = new ZipOutputStream(outputStream);){
	zipOutputStream.putNextEntry(new ZipEntry("writeToZipFile1.txt"));
	BufferedOutputStream bufferedOutputStream = new BufferedOutputStream (zipOutputStream) ;
	bufferedOutputStream.write("writeToZipFile1.txt test中文".getBytes());
	bufferedOutputStream.flush();

	zipOutputStream.putNextEntry(new ZipEntry("writeToZipFile2.txt"));
	bufferedOutputStream.write("writeToZipFile2.txt test中文".getBytes());
	bufferedOutputStream.flush();

	zipOutputStream.putNextEntry(new ZipEntry("writeToZipFile3.txt"));
	bufferedOutputStream.write("writeToZipFile3.txt test中文".getBytes());
	bufferedOutputStream.flush();

	bufferedOutputStream.close();
}