Java IO流是Java中非常重要的一部分，是一個用于訪問文件、網絡等的機制。在Java IO流作業中，常見的問題是如何讀寫文件、如何處理網絡連接等。下面是一些Java IO流作業和答案的示例：

1. 如何打開一個文件并讀寫其中的內容？
下面是代碼示例：
try (FileInputStream fis = new FileInputStream("file.txt");
BufferedInputStream bis = new BufferedInputStream(fis);
FileOutputStream fos = new FileOutputStream("output.txt");
BufferedOutputStream bos = new BufferedOutputStream(fos)) {
byte[] buffer = new byte[4096];
int bytesRead = -1;
while ((bytesRead = bis.read(buffer)) != -1) {
bos.write(buffer, 0, bytesRead);
}
} catch (IOException e) {
e.printStackTrace();
}
2. 如何讀取一個網絡連接的數據？
下面是代碼示例：
try (Socket socket = new Socket("localhost", 8080);
InputStream is = socket.getInputStream();
OutputStream os = socket.getOutputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(os))) {
bw.write("GET / HTTP/1.1\n");
bw.write("Host: localhost\n\n");
bw.flush();
String line = null;
while ((line = br.readLine()) != null) {
System.out.println(line);
}
} catch (IOException e) {
e.printStackTrace();
}
3. 如何將一個文件的內容轉換成一個字符串？
下面是代碼示例：
try (FileInputStream fis = new FileInputStream("file.txt");
BufferedInputStream bis = new BufferedInputStream(fis);
ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
byte[] buffer = new byte[4096];
int bytesRead = -1;
while ((bytesRead = bis.read(buffer)) != -1) {
baos.write(buffer, 0, bytesRead);
}
String content = new String(baos.toByteArray());
} catch (IOException e) {
e.printStackTrace();
}