使用Java修改文件内容 [英] Modify the content of a file using Java

问题描述

我想使用java程序删除文件的一些内容，如下所示.这是在同一文件中替换的写入方法还是应该将其复制到另一个文件中.

I want to delete some content of file using java program as below. Is this the write method to replace in the same file or it should be copied to the another file.

但是它删除了文件的所有内容.

But its deleting the all content of the file.

class FileReplace
{
    ArrayList<String> lines = new ArrayList<String>();
    String line = null;
    public void  doIt()
    {
        try
        {
            File f1 = new File("d:/new folder/t1.htm");
            FileReader fr = new FileReader(f1);
            BufferedReader br = new BufferedReader(fr);
            while (line = br.readLine() != null)
            {
                if (line.contains("java"))
                    line = line.replace("java", " ");
                lines.add(line);
            }
            FileWriter fw = new FileWriter(f1);
            BufferedWriter out = new BufferedWriter(fw);
            out.write(lines.toString());
        }
        catch (Exception ex)
        {
            ex.printStackTrace();
        }
    }
    public statc void main(String args[])
    {
        FileReplace fr = new FileReplace();
        fr.doIt();
    }
}

推荐答案

我会从关闭阅读器和刷新写入器开始:

I would start with closing reader, and flushing writer:

public class FileReplace {
    List<String> lines = new ArrayList<String>();
    String line = null;

    public void  doIt() {
        try {
            File f1 = new File("d:/new folder/t1.htm");
            FileReader fr = new FileReader(f1);
            BufferedReader br = new BufferedReader(fr);
            while ((line = br.readLine()) != null) {
                if (line.contains("java"))
                    line = line.replace("java", " ");
                lines.add(line);
            }
            fr.close();
            br.close();

            FileWriter fw = new FileWriter(f1);
            BufferedWriter out = new BufferedWriter(fw);
            for(String s : lines)
                 out.write(s);
            out.flush();
            out.close();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    public static void main(String args[]) {
        FileReplace fr = new FileReplace();
        fr.doIt();
    }
}

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