使用 DataOutputStream 确定写入文件的字节数的Java程序

Java OutputStream 类， Java.io.OutputStream ，是Java IO API中所有输出流的基类。输出流接受输出字节并将它们发送到某个接收器。需要定义 OutputStream 子类的应用程序必须始终提供至少一种写入一个字节输出的方法。

• 为了获得写入的字节数，我们首先创建一个对象 FileOutputStream通过传递在下面的代码中显示为 FileOS 的文件路径。
• 然后我们通过传递 FileOS 即 FileOutputStream 的对象来创建DataOutputStream的对象，它在下面的代码中显示为 DataOS。
• 现在，我们将使用 DataOutputStream 的writeBytes()方法将文本注入到该文本文件中。为了获得写入的字节大小，我们在对象 DataOS 上使用 DataOutputStream 类的 size 方法。

方案一：

Java

// Java program to determine number of bytes
// written to DataOutputStream
  
import java.io.*;
  
public class NumberOfBytesInOutputStream {
    public static void main(String[] args)
    {
        try {
            
            // creates object of FileOutputStream by passing
            // file Bytes.txt
            FileOutputStream FileOS
                = new FileOutputStream("C:/Bytes.txt");
  
            // creates object of DataOutputStream by
            // passing object of FileOutputStream i.e.
            // FileOS
            DataOutputStream DataOS = new DataOutputStream(FileOS);
  
            // writes the string passed to object of
            // DataOutputStream
            DataOS.writeBytes(
                 "GeeksforGeeks is the best place to learn Coding online.");
  
            // Stores the number of bytes to total_bytes
            // variable using size() method of
            // DataOutputStream class
            int total_bytes = DataOS.size();
  
            // Showing the number of bytes as output in
            // console
            DataOS.close();
  
            System.out.println("Total " + total_bytes
                        + " bytes were written to stream.");
        }
        catch (Exception e) 
        {
            System.out.println("Exception: " + e.toString());
        }
    }
}

输出：

方案二：

Java

// Java program to determine number of bytes
// written to DataOutputStream
  
import java.io.*;
  
public class NumberOfBytesInOutputStream2 {
    public static void main(String[] args)
    {
        try {
            
            // creates object of FileOutputStream by passing
            // file Bytes.txt
            FileOutputStream FileOS = new FileOutputStream("C:/NumberOfBytes.txt");
  
            // creates object of DataOutputStream by passing
            // object of FileOutputStream i.e. FileOS
            DataOutputStream DataOS = new DataOutputStream(FileOS);
  
            // create string S with the desired text
            String S = "GeeksforGeeks article is best for getting cs concepts.";
  
            // writes the string passed to object of
            // DataOutputStream
            DataOS.writeBytes(S);
  
            // Stores the number of bytes to total_bytes
            // variable using size() method of
            // DataOutputStream class
            int total_bytes = DataOS.size();
  
            // Showing the number of bytes as output in
            // console
            System.out.println("Total " + total_bytes
                      + " bytes were written to stream.");
  
            DataOS.close();
            
        }
        catch (Exception e) 
        {
            System.out.println("Exception: " + e.toString());
        }
    }
}

输出：