Java7新特性（二）IO

来源：互联网发布：c语言!= 编辑：程序博客网时间：2024/06/10 08:45

附上：java 7 TWR

5.try-with-resources(TWR) AutoCloseable

package com.java7developer.chapter1;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.MalformedURLException;
import java.net.URL;
public class Java7ResourcesExample {
  private void run() throws IOException {
    File file = new File("foo");
    URL url = null;
    try {
      url = new URL("http://www.google.com/");
    } catch (MalformedURLException e) {
    }
    try (OutputStream out = new FileOutputStream(file);
        InputStream is = url.openStream()) {
      byte[] buf = new byte[4096];
      int len;
      while ((len = is.read(buf)) > 0) {
        out.write(buf, 0, len);
      }
    }
  }
  public static void main(String[] args) throws IOException {
    Java7ResourcesExample instance = new Java7ResourcesExample();
    instance.run();
  }
}

本文主要根据《Java程序员修炼之道》整理的代码笔记片段

1.Path

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//查找目录下文件
Path dir = Paths.get("E:\\Learn\\Java7\\trunk");
try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir,
"*.properties")) {
for (Path entry : stream) {
System.out.println(entry.getFileName());
}
} catch (IOException e) {
System.out.println(e.getMessage());
}

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Path listing = Paths.get("/usr/bin/zip");
System.out.println("File Name [" + listing.getFileName() + "]");
System.out.println("Number of Name Elements in the Path ["
+ listing.getNameCount() + "]");
System.out.println("Parent Path [" + listing.getParent() + "]");
System.out.println("Root of Path [" + listing.getRoot() + "]");
System.out.println("Subpath from Root, 2 elements deep ["
+ listing.subpath(0, 2) + "]");

2.Files.walkFileTree 遍历目录

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public static void main(String[] args) throws IOException {
ath startingDir = Paths.get("E:\\Learn\\Java7\\trunk");
//遍历目录
Files.walkFileTree(startingDir, new FindJavaVisitor());
}
private static class FindJavaVisitor extends SimpleFileVisitor<Path> {
@Override
public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
if (file.toString().endsWith(".java")) {
System.out.println(file.getFileName());
}
return FileVisitResult.CONTINUE;
}
}

3.Files

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try {
Path zip = Paths.get("E:\\java\\test");
//Path zip = Paths.get("E:\\java\\测试.rar");
System.out.println(zip.toAbsolutePath().toString());
System.out.println(Files.getLastModifiedTime(zip));
System.out.println(Files.size(zip));
System.out.println(Files.isSymbolicLink(zip));
System.out.println(Files.isDirectory(zip));
System.out.println(Files.readAttributes(zip, "*"));
} catch (IOException ex) {
System.out.println("Exception" + ex.getMessage());
}

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try {
if(Files.exists(old)){
Files.copy(old, target, StandardCopyOption.REPLACE_EXISTING);
Files.move(old, target2,StandardCopyOption.REPLACE_EXISTING);
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

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Path target = Paths.get("E:\\java\\test1.txt");
// try {
// Files.delete(target);
// } catch (IOException e1) {
// // TODO Auto-generated catch block
// e1.printStackTrace();
// }
Set<PosixFilePermission> perms =
PosixFilePermissions.fromString("rw-rw-rw-");
//FileAttribute<Set<PosixFilePermission>> attr =
PosixFilePermissions.asFileAttribute(perms);
try {
if(Files.notExists(target)){
Files.createFile(target);
}
} catch (IOException e) {
e.printStackTrace();
}

4.读文件

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Path old = Paths.get("E:\\java\\test.txt");
Path target = Paths.get("E:\\java\\test\\test1.txt");
try (BufferedReader reader = Files.newBufferedReader(old, StandardCharsets.UTF_8)){
String line ;
while((line = reader.readLine())!=null){
System.out.println(line);
}
} catch (IOException e) {
}
try(BufferedWriter writer =
Files.newBufferedWriter(target, StandardCharsets.UTF_8, StandardOpenOption.WRITE)){
writer.write("hello");
} catch (IOException e) {
e.printStackTrace();
}
try {
@SuppressWarnings("unused")
List<String> lines = Files.readAllLines(old, StandardCharsets.UTF_8);
@SuppressWarnings("unused")
byte[] bytes = Files.readAllBytes(old);
} catch (IOException e) {
e.printStackTrace();
}
}

5.监听目录变化

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//监听目录变化
try {
WatchService watcher = FileSystems.getDefault().newWatchService();
Path dir = FileSystems.getDefault().getPath("E:\\java");
WatchKey key = dir.register(watcher, ENTRY_MODIFY);
while (!shutdown) {
key = watcher.take();
for (WatchEvent<?> event : key.pollEvents()) {
if (event.kind() == ENTRY_MODIFY) {
System.out.println("Home dir changed!");
}
}
key.reset();
}
} catch (IOException | InterruptedException e) {
System.out.println(e.getMessage());
}

6.FileChannel通道截取

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try {
Path file = Paths.get("E:\\java\\test.txt");
FileChannel channel = FileChannel.open(file);
ByteBuffer buffer = ByteBuffer.allocate(1024);
channel.read(buffer, channel.size() -13);
tem.out.println((char)buffer.array()[0]);
} catch (IOException e) {
System.out.println(e.getMessage());
}

7.AsynchronousFileChannel 异步通道读取

将来式

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public class Listing_2_8 {
//将来式
public static void main(String[] args) {
try {
Path file = Paths.get("E:\\java\\test.txt");
AsynchronousFileChannel channel = AsynchronousFileChannel.open(file);
ByteBuffer buffer = ByteBuffer.allocate(100_000);
Future<Integer> result = channel.read(buffer, 0);
while (!result.isDone()) {
ProfitCalculator.calculateTax();
}
Integer bytesRead = result.get();
System.out.println("Bytes read [" + bytesRead + "]");
} catch (IOException | ExecutionException | InterruptedException e) {
System.out.println(e.getMessage());
}
}
private static class ProfitCalculator {
@SuppressWarnings("unused")
public ProfitCalculator() {
}
public static void calculateTax() {
System.out.println("test");
}
}
}

回调式

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public class Listing_2_9 {
//回调式
public static void main(String[] args) {
try {
Path file = Paths.get("E:\\java\\test.txt");
AsynchronousFileChannel channel = AsynchronousFileChannel.open(file);
ByteBuffer buffer = ByteBuffer.allocate(100_000);
channel.read(buffer, 0, buffer,
new CompletionHandler<Integer, ByteBuffer>() {
public void completed(Integer result, ByteBuffer attachment) {
//System.out.println("read");
System.out.println("Bytes read [" + result + "]");
}
public void failed(Throwable exception, ByteBuffer attachment) {
System.out.println(exception.getMessage());
}
});
// System.out.println("test");
Thread.sleep(1000);
} catch (IOException | InterruptedException e) {
System.out.println(e.getMessage());
}
}
}

8.NetworkChannel 非阻塞网络套接字

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SelectorProvider provider = SelectorProvider.provider();
try {
NetworkChannel socketChannel = provider.openSocketChannel();
SocketAddress address = new InetSocketAddress(3080);
socketChannel = socketChannel.bind(address);
Set<SocketOption<?>> socketOptions = socketChannel.supportedOptions();
System.out.println(socketOptions.toString());
socketChannel.setOption(StandardSocketOptions.IP_TOS, 3);
//System.out.println(socketChannel.getOption(StandardSocketOptions.IP_TOS));
Boolean keepAlive = socketChannel
.getOption(StandardSocketOptions.SO_KEEPALIVE);
// System.out.println(keepAlive);
} catch (IOException e) {
System.out.println(e.getMessage());
}

其他：MulticastChannel Files.setPosixFilePermissions Files.readSymbolicLink Files.readAttributes(file, BasicFileAttributes.class);

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