Question

我正在制作一个节目来存储歌曲＆＃39;标题，艺术家和流派进入数据文件。像这样：

    public void writeSong(Song t) throws IOException {
    File myFile = new File(Song.getFileInput());
    RandomAccessFile write = new RandomAccessFile(myFile,"rw");
    write.writeChars(title);
    write.writeChars(artist);
    write.writeChars(genre);
    write.close();
}

在我这样做之后，我应该读取数据文件并显示它的内容，如下所示：

    public Song readSong() throws FileNotFoundException, IOException {

    File myFile = new File(Song.getFileInput());
    RandomAccessFile read = new RandomAccessFile(myFile, "rw");
    String readTitle = null, readArtist = null, readGenre = null;
    Song so = null;

    read.seek(0);
    for(int i = 0; i < title.length(); i++){
        readTitle += read.readChar();
    }

    read.seek(50);
    for(int i = 0; i < artist.length(); i++){
        readArtist += read.readChar();
    }

    read.seek(100);
    for(int i = 0; i < genre.length(); i++){
        readGenre += read.readChar();
    }

    so = new Song(readTitle, readArtist, readGenre);
    read.close();
    return so;
}

如果我将它分配给名为＆＃34; songs.dat＆＃34;的文件，它应该写下并读取该文件中的歌曲。退出程序并再次运行后，我将文件命名为＆＃34; songs.dat＆＃34;再次。但是当我想阅读和显示歌曲时，没有任何反应。有人如何解决这个问题？

Answer 1

RandomAccessFile.seek(long position)设置要读取或写入的文件位置。

当您开始阅读文件时，您使用read.seek(0)将位置设置为0。但是从那里你不需要重置它：

public Song readSong() throws FileNotFoundException, IOException {

    File myFile = new File(Song.getFileInput());
    RandomAccessFile read = new RandomAccessFile(myFile, "rw");
    String readTitle = "", readArtist = "", readGenre = "";
    Song so = null;

    read.seek(0);
    for(int i = 0; i < title.length(); i++){
        readTitle += read.readChar();
    }

    for(int i = 0; i < artist.length(); i++){
        readArtist += read.readChar();
    }

    for(int i = 0; i < genre.length(); i++){
        readGenre += read.readChar();
    }

    so = new Song(readTitle, readArtist, readGenre);
    read.close();
    return so;
}

我也将你的String初始化为空字符串，这样你就没有＆＃34; null＆＃34;结果首先是字符串

运行程序一次后保留一个值？

1 个答案: