java foundation - random access streaming

package stream;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;

import org.junit.jupiter.api.Test;



/*
 * RandomAccessFile: random read and write access streaming
 * Either an input stream or an output stream
 * R | w | d | s: Read | Write | update data | metadata updates 
 *     
 * W: is the beginning of the file content coverage
 * 
 * */

public class RandomAccessFileTest {
    
    @Test
    public void test1(){
        
        RandomAccessFile raf1 = null;
        RandomAccessFile raf2 = null;
        try {
            //1.流对象
            raf1 = new RandomAccessFile(new File("hello.txt"),"r");
            raf2 = new RandomAccessFile(new File("hello2.txt"),"rw");
            
            //2.读写
            byte[]     buffer = new byte[1024];
            int len;
            while((len = raf1.read(buffer))!=-1) {
                raf2.write(buffer,0,len);
            }
        } catch (Exception e) {
            
            e.printStackTrace ();
        }
        finally {
            try {
                if(raf1!=null)
                    raf1.close();
            } catch (Exception e) {
                e.printStackTrace ();
            }
            try {
                if(raf2!=null)
                    raf2.close();
            } catch (Exception e) {
                e.printStackTrace ();
            }
        }
    }
    
    /*
     * Seek random access | insertion method
     * 
     * */
    @Test
    public void test2() throws IOException {
        RandomAccessFile raf1 = new RandomAccessFile("hello.txt", "rw");
        /*raf1.seek(3); 
        raf1.write("abc".getBytes());
        */
        
        /*
         * Use StringBuilder
         * */
        StringBuilder sb = new StringBuilder((int)(new File("hello.txt").length()));
        raf1.seek ( 3L );
         int len;
         byte [] Buffer = new new  byte [ 20 is ];
         // to save it back to 
        the while ((len = raf1.read (Buffer)) = -! . 1 ) {
            sb.append(new String(buffer,0,len));
        }
        
        raf1.seek ( 3L );
         // converted to byte write 
        raf1.write ( " Zhouen Jie " .getBytes ());
        raf1.write(sb.toString().getBytes());
        raf1.close();
    }
}