///////    TextLines.java    ///////
import java.io.*;
import java.util.Vector;

class TextLines
{  TextLines() { this(16); }
   TextLines(int len) { lines = new Vector(len); }

   StringBuffer getLine(int i)
   {  return( (i>=0 && i<lines.size())
               ? (StringBuffer) lines.elementAt(i) : null ); 
   }

   public void setLine(StringBuffer b, int k)  // sets line k to b
   {    lines.setElementAt(b,k);
   }

   public void setLine(String l, int k)  // sets line k to l
   {    lines.setElementAt(new StringBuffer(l),k) ;
   }

   public void addLine(StringBuffer b)  // adds the given line b
   {    lines.addElement(b);
   }

   public void addLine(String l)  // adds the given line l
   {    lines.addElement(new StringBuffer(l));
   }

   public void delLine(int i)     // delete line i
   {     if ( i > -1 && i < lines.size() )
              lines.removeElementAt(i);
   }

   public int length() {  return lines.size();  }

   public void swap(int i, int j)      // interchange lines
   {  if ( i > -1 && j > -1 && i < lines.size()
           && j < lines.size() )
      {   Object tmp = lines.elementAt(i);
          lines.setElementAt(lines.elementAt(j), i) ;
          lines.setElementAt(tmp, j);
      }
   }

   public int input(InputStream in)
   {   String s;
       BufferedReader rdr = new BufferedReader
                         (new InputStreamReader(in));
       try
       {  while ( (s = rdr.readLine() ) != null )
               addLine(s);
       } catch ( IOException e )
         {  System.err.println(
               "TextLines: Error reading input");
            return(-1);
         }
       return lines.size();  // number of lines read
   }

   public void output(OutputStream out)
   {   int i=0;
       PrintWriter o = new PrintWriter
           (new BufferedWriter(new OutputStreamWriter(out)));
       while( i < lines.size() )
       {   o.println(lines.elementAt(i++));  }
       o.flush();
   }

   private Vector lines;
}