Exception in thread main

Juan Manuel Casta?
18 de Junio del 2009
Eclipse me devuelve mesnaje cuando hago debug con una Debug Configuration para Lectura.NoCadena.
package Lectura;
import java.io.DataInputStream;
import java.io.IOException;

public class NoCadena extends DataInputStream{
static NoCadena nocadena=null;

private NoCadena(java.io.InputStream is){
super(is);
}
public static NoCadena crear(){

if(NoCadena.nocadena==null)NoCadena.nocadena=new NoCadena(System.in);
return nocadena;
}
public Object clone(){return this;}
public byte leerByte() throws IOException{

return this.readByte();

}
public boolean leerBoolean()throws IOException{
return this.readBoolean();
}
public double leerDouble()throws IOException {
return this.readDouble();}
public char leerCaracter()throws IOException{return super.readChar();}
public float leerFloat()throws IOException{return super.readFloat();}
public int leerInt()throws IOException{return this.readInt();}
public long leerLong() throws IOException{return super.readLong();}
public short leerShort() throws IOException{return super.readShort();}
}
¿Por qué?¿Cómo se soluciona?