RandomAccessFile操作文件

 package file;

 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.RandomAccessFile;

 public class InsertContent {

     public static void insert(String fileName,long pos,String insertContent) throws IOException{
         File tmp = File.createTempFile("tmp", null);
         tmp.deleteOnExit();
         try(
             RandomAccessFile raf = new RandomAccessFile(fileName, "rw");
             FileOutputStream tmpOut = new FileOutputStream(tmp);
             FileInputStream tmpInputStream = new FileInputStream(tmp)
             ){
             //  将记录指针移动文件末尾  追加内容
 //            raf.seek(raf.length());

             // 将记录指针移动指定位置
             raf.seek(pos);

             byte[] bbuf = new byte[64];

             int hasRead = 0;

             StringBuffer sbf = new StringBuffer();

             while((hasRead = raf.read(bbuf)) > 0 ){
                 tmpOut.write(bbuf, 0 , hasRead);
                 sbf.append(new String(bbuf));
             }
             System.out.println(sbf.toString());

             raf.seek(pos);

             raf.write(insertContent.getBytes());

             while ((hasRead = tmpInputStream.read(bbuf)) > 0) {
                 raf.write(bbuf , 0 , hasRead);
             }
         }
     }

     public static void main(String[] args) {
         try {
             insert("f:/new 1.txt", 45, "ajsdkjfksldjfkl");
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 }