java附加文件的操作有以下几种方式：

1. 使用FileWriter附加内容到文件；
2. 使用BufferedWriter将内容附加到文件；
3. 使用PrintWriter将文本附加内容到文件；
4. 使用FileOutputStream附加内容到文件；

注意事项: 
       处理文本文件，笔者建议使用FileWriter，当写入数据量大时，建议使用BufferedWriter
  处理二进制文件，建议使用FileOutputStream 

方式一： 使用FileWriter附加到文件

例:

File file = new File("java265.txt");
FileWriter fr = new FileWriter(file, true);
fr.write("the website is Java265.txt");
fr.close();

方式二： 使用BufferedWriter将内容附加到现有文件

File file = new File("java265.txt");
FileWriter fr = new FileWriter(file, true);
BufferedWriter br = new BufferedWriter(fr);
br.write("the website is Java265.txt");
br.close();
fr.close();

方式三： 使用PrintWriter将文本附加内容到文件

File file = new File("java265.txt");
FileWriter fr = new FileWriter(file, true);
BufferedWriter br = new BufferedWriter(fr);
PrintWriter pr = new PrintWriter(br);
pr.println("the website is Java265.txt");
pr.close();
br.close();
fr.close();

方式四： 使用FileOutputStream追加到文件

     当原始数据，二进制数据，图像，视频等应该使用FileOutputStream将数据附加到文件中

OutputStream os = new FileOutputStream(new File("java265.txt"), true);
os.write("the website is Java265.txt".getBytes(), 0, "the website is Java265.txt".length());
os.close();

例:Java附加到文件 

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

public class testClass{

    /**
     * 将内容附加到文件的示例
     * 
     * @param args
     */
    public static void main(String[] args) {
        String filePath = "D:/tmp/java265.txt";

        String appendText = "the website is java265.com";

        appendUsingFileWriter(filePath, appendText);

        appendUsingBufferedWriter(filePath, appendText, 2);

        appendUsingPrintWriter(filePath, appendText);

        appendUsingFileOutputStream(filePath, appendText);
    }

    private static void appendUsingPrintWriter(String filePath, String text) {
        File file = new File(filePath);
        FileWriter fr = null;
        BufferedWriter br = null;
        PrintWriter pr = null;
        try {
            // 要附加到文件，需要使用下面的构造函数初始化FileWriter
            fr = new FileWriter(file, true);
            br = new BufferedWriter(fr);
            pr = new PrintWriter(br);
            pr.println(text);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                pr.close();
                br.close();
                fr.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

  
    private static void appendUsingFileOutputStream(String fileName, String data) {
        OutputStream os = null;
        try {
            // 下面true标志告诉OutputStream追加
            os = new FileOutputStream(new File(fileName), true);
            os.write(data.getBytes(), 0, data.length());
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                os.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    
    private static void appendUsingBufferedWriter(String filePath, String text, int noOfLines) {
        File file = new File(filePath);
        FileWriter fr = null;
        BufferedWriter br = null;
        try {
            // 要附加到文件，需要使用下面的构造函数初始化FileWriter
            fr = new FileWriter(file, true);
            br = new BufferedWriter(fr);
            for (int i = 0; i < noOfLines; i++) {
                br.newLine();
                // you can use write or append method
                br.write(text);
            }

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                br.close();
                fr.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

   
    private static void appendUsingFileWriter(String filePath, String text) {
        File file = new File(filePath);
        FileWriter fr = null;
        try {
            // 下面的构造函数参数决定是追加还是覆盖
            fr = new FileWriter(file, true);
            fr.write(text);

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                fr.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}