java 怎样向一个已存在的文件中添加内容

如果想向某个文件最后添加内容，可使用FileWriter fw = new FileWriter("log.txt",true);在创建FileWriter时加个true就可以了。

下面是详细的示例代码：

File file = new File("D:/Test.txt");
File dest = new File("D:/new.txt");
try {
    BufferedReader reader = new BufferedReader(new FileReader(file));
    BufferedWriter writer  = new BufferedWriter(new FileWriter(dest,true));
    String line = reader.readLine();
    while(line!=null){
        writer.write(line);
        line = reader.readLine();
    }
    writer.flush();
    reader.close();
    writer.close();
} catch (FileNotFoundException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
}