Java IO流与NIO技术综合应用详细实例代码
作者：爪哇学长
这篇文章主要给大家介绍了关于Java IO流与NIO技术综合应用的相关资料,文中包括了字节流和字符流,以及它们的高级特性如缓冲区、序列化和反序列化,同时还介绍了NIO中的通道和缓冲区,以及选择器的使用,需要的朋友可以参考下
字节流
输入流（InputStream）
FileInputStream：从文件系统中读取原始字节
import java.io.FileInputStream;
import java.io.IOException;
public class ReadFileBytes {
public static void main(String[] args) {
try (FileInputStream fis = new FileInputStream("input.txt")) {
int content;
while ((content = fis.read()) != -1) {
System.out.print((char) content);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
ByteArrayInputStream：允许程序从一个字节数组中读取数据
import java.io.ByteArrayInputStream;
public class ReadByteArray {
public static void main(String[] args) {
byte[] buffer = "Hello, World!".getBytes();
try (ByteArrayInputStream bis = new ByteArrayInputStream(buffer)) {
int data;
while ((data = bis.read()) != -1) {
System.out.print((char) data);
}
}
}
}
BufferedInputStream：为其他输入流添加缓冲功能
import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.IOException;
public class BufferedRead {
public static void main(String[] args) {
try (BufferedInputStream bis = new BufferedInputStream(new FileInputStream("input.txt"))) {
int content;
while ((content = bis.read()) != -1) {
System.out.print((char) content);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
ObjectInputStream：用于反序列化对象
import java.io.ObjectInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.Serializable;
class Person implements Serializable {
private static final long serialVersionUID = 1L;
String name;
Person(String name) {
this.name = name;
}
}
public class DeserializeObject {
public static void main(String[] args) {
try (ObjectInputStream ois = new ObjectInputStream(new FileInputStream("person.ser"))) {
Person person = (Person) ois.readObject();
System.out.println(person.name);
} catch (IOException | ClassNotFoundException e) {
e.printStackTrace();
}
}
}
输出流（OutputStream）
FileOutputStream：向文件系统中的文件写入原始字节
import java.io.FileOutputStream;
import java.io.IOException;
public class WriteFileBytes {
public static void main(String[] args) {
String data = "Hello, World!";
byte[] buffer = data.getBytes();
try (FileOutputStream fos = new FileOutputStream("output.txt")) {
fos.write(buffer);
} catch (IOException e) {
e.printStackTrace();
}
}
}
ByteArrayOutputStream：将输出的数据写入到字节数组中
import java.io.ByteArrayOutputStream;
public class WriteByteArray {
public static void main(String[] args) {
String data = "Hello, World!";
byte[] buffer = data.getBytes();
try (ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
baos.write(buffer);
byte[] output = baos.toByteArray();
System.out.println(new String(output));
}
}
}
BufferedOutputStream：为其他输出流提供缓冲区
import java.io.BufferedOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class BufferedWrite {
public static void main(String[] args) {
String data = "Hello, World!\n";
byte[] buffer = data.getBytes();
try (BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("output.txt"))) {
bos.write(buffer);
} catch (IOException e) {
e.printStackTrace();
}
}
}
ObjectOutputStream：用于序列化对象
import java.io.ObjectOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.Serializable;
class Person implements Serializable {
private static final long serialVersionUID = 1L;
String name;
Person(String name) {
this.name = name;
}
}
public class SerializeObject {
public static void main(String[] args) {
Person person = new Person("Alice");
try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("person.ser"))) {
oos.writeObject(person);
} catch (IOException e) {
e.printStackTrace();
}
}
}
字符流
输入流（Reader）
FileReader：简化了从文件读取字符的过程
import java.io.FileReader;
import java.io.BufferedReader;
import java.io.IOException;
public class ReadFileChars {
public static void main(String[] args) {
try (BufferedReader reader = new BufferedReader(new FileReader("input.txt"))) {
String line;
while ((line = reader.readLine()) != null) {
System.out.println(line);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
CharArrayReader：从字符数组中读取字符
import java.io.CharArrayReader;
public class ReadCharArray {
public static void main(String[] args) {
char[] chars = "Hello, World!".toCharArray();
try (CharArrayReader car = new CharArrayReader(chars)) {
int c;
while ((c = car.read()) != -1) {
System.out.print((char) c);
}
}
}
}
BufferedReader：为其他字符输入流添加缓冲区
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class BufferedCharRead {
public static void main(String[] args) {
try (BufferedReader br = new BufferedReader(new FileReader("input.txt"))) {
String line;
while ((line = br.readLine()) != null) {
System.out.println(line);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
InputStreamReader：桥接器，将字节流转换为字符流
import java.io.InputStreamReader;
import java.io.FileInputStream;
import java.io.IOException;
public class ByteToChar {
public static void main(String[] args) {
try (InputStreamReader isr = new InputStreamReader(new FileInputStream("input.txt"), "UTF-8")) {
int c;
while ((c = isr.read()) != -1) {
System.out.print((char) c);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
输出流（Writer）
FileWriter：简化了将字符写入文件的过程
import java.io.FileWriter;
import java.io.IOException;
public class WriteFileChars {
public static void main(String[] args) {
String data = "Hello, World!\n";
try (FileWriter writer = new FileWriter("output.txt", true)) { // 追加模式
writer.write(data);
} catch (IOException e) {
e.printStackTrace();
}
}
}
CharArrayWriter：将字符写入字符数组
import java.io.CharArrayWriter;
public class WriteCharArray {
public static void main(String[] args) {
String data = "Hello, World!";
try (CharArrayWriter caw = new CharArrayWriter()) {
caw.write(data);
char[] output = caw.toCharArray();
System.out.println(new String(output));
}
}
}
BufferedWriter：为其他字符输出流添加缓冲区
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
public class BufferedCharWrite {
public static void main(String[] args) {
String data = "Hello, World!\n";
try (BufferedWriter bw = new BufferedWriter(new FileWriter("output.txt", true))) {
bw.write(data);
bw.newLine(); // 写入换行符
} catch (IOException e) {
e.printStackTrace();
}
}
}
OutputStreamWriter：桥接器，将字符流转换为字节流
import java.io.OutputStreamWriter;
import java.io.FileOutputStream;
import java.io.IOException;
public class CharToByte {
public static void main(String[] args) {
String data = "Hello, World!";
try (OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("output.txt"), "UTF-8")) {
osw.write(data);
} catch (IOException e) {
e.printStackTrace();
}
}
}
高级特性
Piped Streams：管道流使得一个线程可以通过管道将数据发送给另一个线程
import java.io.PipedInputStream;
import java.io.PipedOutputStream;
import java.io.IOException;
class Producer implements Runnable {
private PipedOutputStream pos;
Producer(PipedInputStream pis) throws IOException {
pos = new PipedOutputStream(pis);
}
@Override
public void run() {
try {
String data = "Hello, Pipe!";
pos.write(data.getBytes());
pos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
class Consumer implements Runnable {
private PipedInputStream pis;
Consumer(PipedOutputStream pos) throws IOException {
pis = new PipedInputStream(pos);
}
@Override
public void run() {
try {
int data;
while ((data = pis.read()) != -1) {
System.out.print((char) data);
}
pis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public class PipeStreams {
public static void main(String[] args) throws IOException {
PipedInputStream pis = new PipedInputStream();
PipedOutputStream pos = new PipedOutputStream(pis);
Thread producerThread = new Thread(new Producer(pos));
Thread consumerThread = new Thread(new Consumer(pis));
producerThread.start();
consumerThread.start();
}
}
PrintStream：格式化输出流，通常用于标准输出（控制台）
import java.io.PrintStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class UsePrintStream {
public static void main(String[] args) {
try (PrintStream ps = new PrintStream(new FileOutputStream("output.txt"))) {
ps.println("Hello, PrintStream!");
ps.printf("This is a formatted string: %d%%\n", 100);
} catch (IOException e) {
e.printStackTrace();
}
}
}
Scanner：用于解析基础数据类型和字符串
import java.util.Scanner;
import java.io.File;
import java.io.IOException;
public class UseScanner {
public static void main(String[] args) {
try (Scanner scanner = new Scanner(new File("input.txt"))) {
while (scanner.hasNextLine()) {
String line = scanner.nextLine();
System.out.println(line);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
Formatter：用于格式化输出
import java.io.PrintWriter;
import java.io.StringWriter;
public class UseFormatter {
public static void main(String[] args) {
StringWriter sw = new StringWriter();
PrintWriter pw = new PrintWriter(sw);
pw.format("Hello, %s!\n", "Formatter");
pw.format("Formatted integer: %d\n", 42);
System.out.println(sw.toString());
}
}
NIO (New IO)
Channels 和 Buffers
使用FileChannel和ByteBuffer读写文件
import java.nio.file.Paths;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.nio.channels.FileChannel;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.io.IOException;
public class NIOExample {
public static void main(String[] args) {
Path path = Paths.get("output.txt");
String data = "Hello NIO!";
// Writing to file using FileChannel and ByteBuffer
try (FileChannel channel = FileChannel.open(path, StandardOpenOption.CREATE, StandardOpenOption.WRITE)) {
ByteBuffer buffer = ByteBuffer.allocate(1024);
buffer.put(data.getBytes(StandardCharsets.UTF_8));
buffer.flip(); // Switch to read mode
channel.write(buffer);
} catch (IOException e) {
e.printStackTrace();
}
// Reading from file using FileChannel and ByteBuffer
try (FileChannel channel = FileChannel.open(path)) {
ByteBuffer buffer = ByteBuffer.allocate(1024);
int bytesRead = channel.read(buffer);
buffer.flip(); // Switch to read mode
byte[] bytes = new byte[bytesRead];
buffer.get(bytes);
System.out.println(new String(bytes, StandardCharsets.UTF_8));
} catch (IOException e) {
e.printStackTrace();
}
}
}
Selectors
选择器的使用稍微复杂一些，它主要用于网络编程中，以实现非阻塞I/O。这里提供一个简单的例子来展示如何创建和使用选择器监控多个SocketChannel。
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.channels.spi.SelectorProvider;
public class SelectorExample {
public static void main(String[] args) throws IOException {
// Open a selector
Selector selector = SelectorProvider.provider().openSelector();
// Open a server socket channel and bind it to port 8080
ServerSocketChannel serverChannel = ServerSocketChannel.open();
serverChannel.socket().bind(new InetSocketAddress(8080));
serverChannel.configureBlocking(false);
// Register the server channel with the selector for accepting connections
serverChannel.register(selector, SelectionKey.OP_ACCEPT);
// Loop indefinitely, waiting for events on the channels registered with the selector
while (true) {
// Wait for at least one event
selector.select();
// Get the set of keys with pending events
for (SelectionKey key : selector.selectedKeys()) {
// Remove the current key from the set so it won't be processed again
selector.selectedKeys().remove(key);
if (!key.isValid()) {
continue;
}
// Check what event is ready and handle it
if (key.isAcceptable()) {
// Accept the new connection
ServerSocketChannel ssc = (ServerSocketChannel) key.channel();
SocketChannel sc = ssc.accept();
sc.configureBlocking(false);
// Register the new SocketChannel with the selector for reading
sc.register(selector, SelectionKey.OP_READ);
} else if (key.isReadable()) {
// Read the data from the client
SocketChannel sc = (SocketChannel) key.channel();
// ... handle reading ...
}
}
}
}
}总结
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