fileinputstream的read和write

FileInputStream (文件输入流) 和 FileOutputStream (文件输出流) 是Java标准库中的两个用于处理文件I/O操作的类。它们都是InputStream和OutputStream的子类，分别用于读取和写入文件。

**FileInputStream.read()**: 这是一个字节读取方法，它从文件中读取数据并返回一个0到255范围内的整数，表示读取的字节值。如果到达文件末尾，会返回-1。如果发生错误，如IO异常，将抛出IOException。例如：

int byteRead = fis.read(); // 一次读取一个字节

**FileOutputStream.write()**: 这是一个字节写入方法，接收一个整数作为参数，代表要写入文件的字节值。它将该字节写入到当前指定位臵，然后移动到下一个位置。同样，如果发生IO错误，会抛出IOException。示例：

fos.write('A'); // 写入字符'A'

这两个类通常与BufferedReader和BufferedWriter等包装类一起使用，以提供更方便的文本读写操作，并处理缓冲和错误处理。

相关问题

Implement the constructor and the read() method in the ChangeToUpperCaseInputStream class. The constructor should call the constructor of the superclass and the read() method should read the data using the superclass's read() method and convert it to upper case before returning it. Right-click on the project name again and select "New -> Java Class". Name the class "ChangeToUpperCaseOutputStream" and make sure to select "extends FilterOutputStream" as the superclass. Implement the constructor and the write() method in the ChangeToUpperCaseOutputStream class. The constructor should call the constructor of the superclass and the write() method should convert the data to upper case before calling the superclass's write() method to write it to the output stream. Once you have implemented these classes, you can use them in your main program by creating an instance of the ChangeToUpperCaseInputStream or ChangeToUpperCaseOutputStream and passing it to your FileInputStream or FileOutputStream, respectively. This will allow you to read or write data in upper case.

Sure, here is an example implementation of the ChangeToUpperCaseInputStream and ChangeToUpperCaseOutputStream classes:

import java.io.*;

public class ChangeToUpperCaseInputStream extends FilterInputStream {

    public ChangeToUpperCaseInputStream(InputStream in) {
        super(in);
    }

    @Override
    public int read() throws IOException {
        int c = super.read();
        return (c == -1 ? c : Character.toUpperCase((char) c));
    }
}

public class ChangeToUpperCaseOutputStream extends FilterOutputStream {

    public ChangeToUpperCaseOutputStream(OutputStream out) {
        super(out);
    }

    @Override
    public void write(int b) throws IOException {
        super.write(Character.toUpperCase((char) b));
    }
}

In the above code, the ChangeToUpperCaseInputStream class extends FilterInputStream and overrides the read() method to read the data using the superclass's read() method and convert it to upper case before returning it. Similarly, the ChangeToUpperCaseOutputStream class extends FilterOutputStream and overrides the write() method to convert the data to upper case before calling the superclass's write() method to write it to the output stream.

To use these classes in your main program, you can create an instance of ChangeToUpperCaseInputStream or ChangeToUpperCaseOutputStream and pass it to your FileInputStream or FileOutputStream, respectively. Here is an example:

import java.io.*;

public class MyProgram {
    public static void main(String[] args) throws IOException {
        FileInputStream in = new FileInputStream("input.txt");
        ChangeToUpperCaseInputStream upperCaseIn = new ChangeToUpperCaseInputStream(in);
        
        FileOutputStream out = new FileOutputStream("output.txt");
        ChangeToUpperCaseOutputStream upperCaseOut = new ChangeToUpperCaseOutputStream(out);
        
        int c;
        while ((c = upperCaseIn.read()) != -1) {
            upperCaseOut.write(c);
        }
        
        upperCaseIn.close();
        upperCaseOut.close();
    }
}

In the above code, we first create a FileInputStream and wrap it in a ChangeToUpperCaseInputStream. We also create a FileOutputStream and wrap it in a ChangeToUpperCaseOutputStream. We then read data from the input stream using the read() method of the ChangeToUpperCaseInputStream and write data to the output stream using the write() method of the ChangeToUpperCaseOutputStream. Finally, we close both streams to release any resources they are holding.

Write a read/write using Android internal storage

To read and write data using Android internal storage, you can follow these steps:

1. Get the application context:

Context context = getApplicationContext();

2. Create a file object with the file name and path:

File file = new File(context.getFilesDir(), "filename.txt");

3. To write data to the file, create a FileOutputStream object and write the data to it:

String data = "Hello, World!";
FileOutputStream outputStream = new FileOutputStream(file);
outputStream.write(data.getBytes());
outputStream.close();

4. To read data from the file, create a FileInputStream object and read the data from it:

FileInputStream inputStream = new FileInputStream(file);
byte[] bytes = new byte[(int) file.length()];
inputStream.read(bytes);
inputStream.close();
String data = new String(bytes);

Note that you should always check for exceptions when reading and writing files. Also, it's important to remember that data stored in internal storage is only accessible to your application and cannot be accessed by other applications or users.