Java IO 内容附加到文件

在本教程中，我们将学习如何使用 Java 将内容附加到文件中。有两种方法可以追加：

1）使用FileWriter和BufferedWriter：在这种方法中，我们将在一个或多个字符串中包含内容，我们将把这些字符串附加到文件中。该文件可以单独使用FileWriter附加，但使用BufferedWriter可以在维护缓冲区时提高性能。

2）使用PrintWriter：这是将内容附加到文件的最佳方式之一。无论你使用PrintWriter对象写什么都会附加到文件中。

使用FileWriter和BufferedWriter将内容附加到File

import java.io.File;
import java.io.FileWriter;
import java.io.BufferedWriter;
import java.io.IOException;

class AppendFileDemo
{
   public static void main( String[] args )
   {    
      try{
        String content = "This is my content which would be appended " +
            "at the end of the specified file";
        //Specify the file name and path here
        File file =new File("C://myfile.txt");

        /* This logic is to create the file if the
         * file is not already present
         */
        if(!file.exists()){
           file.createNewFile();
        }

        //Here true is to append the content to file
        FileWriter fw = new FileWriter(file,true);
        //BufferedWriter writer give better performance
        BufferedWriter bw = new BufferedWriter(fw);
        bw.write(content);
        //Closing BufferedWriter Stream
        bw.close();

    System.out.println("Data successfully appended at the end of file");

      }catch(IOException ioe){
         System.out.println("Exception occurred:");
         ioe.printStackTrace();
       }
   }
}

输出：

Data successfully appended at the end of file

让我们说myfile.txt的内容是：

This is the already present content of my file

运行上述程序后，内容将是：

This is the already present content of my fileThis is my content which 
would be appended at the end of the specified file

使用PrintWriter将内容附加到File

PrintWriter为您提供更大的灵活性。使用此功能，您可以轻松格式化要附加到File的内容。

import java.io.File;
import java.io.FileWriter;
import java.io.PrintWriter;
import java.io.BufferedWriter;
import java.io.IOException;

class AppendFileDemo2
{
   public static void main( String[] args )
   {    
      try{
          File file =new File("C://myfile.txt");
          if(!file.exists()){
            file.createNewFile();
          }
          FileWriter fw = new FileWriter(file,true);
          BufferedWriter bw = new BufferedWriter(fw);
          PrintWriter pw = new PrintWriter(bw);
          //This will add a new line to the file content
          pw.println("");
          /* Below three statements would add three 
           * mentioned Strings to the file in new lines.
           */
          pw.println("This is first line");
          pw.println("This is the second line");
          pw.println("This is third line");
          pw.close();

      System.out.println("Data successfully appended at the end of file");

       }catch(IOException ioe){
           System.out.println("Exception occurred:");
           ioe.printStackTrace();
      }
   }
}

输出：

Data successfully appended at the end of file

让我们说myfile.txt的内容是：

This is the already present content of my file

运行上述程序后，内容将是：

This is the already present content of my file
This is first line
This is the second line
This is third line