随机流-RandomAccessFile

RandomAccessFile 基本操作

案例

import java.io.*;

public class TestMain09 {
    public static void main(String[] args) throws Exception {
        insert("D:\\home\\product\\aa.txt",2,"ni");
    }

    public static   void   insert(String filename,long pos,String insertContent) throws Exception {
        File file = new File("D:\\home\\product\\aa.txt");
        RandomAccessFile raf = null;
        File tmp =new File("D:\\home\\product\\bb.txt");
        FileOutputStream tmpOut = null;
        FileInputStream tmpIn = null;
     //   tmp.deleteOnExit();
        raf = new RandomAccessFile(filename,"rw");
        tmpOut = new FileOutputStream(tmp);
        tmpIn = new FileInputStream(tmp);
        raf.seek(pos);
        byte[] bbuf = new byte[64];
        int hasRead = 0;
        //使用循环方式读取插入点后的数据
        while ((hasRead = raf.read(bbuf)) > 0) {
            System.out.println(hasRead);

            //将读取的数据写入临时文件
            tmpOut.write(bbuf, 0, hasRead);
        }
        //----------下面代码插入内容----------
        //把文件记录指针重新定位到pos位置
        raf.seek(pos);
        //追加需要插入的内容
        raf.write(insertContent.getBytes());
        //追加临时文件中的内容
        while ((hasRead = tmpIn.read(bbuf)) > 0) {
            System.out.println(hasRead);
            raf.write(bbuf, 0, hasRead);
        }
    }
}

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随机流可以做断点续传和指定位置读取文件或插入内容

可参考