weka.core.converters
Interface Loader

All Superinterfaces:
java.io.Serializable
All Known Implementing Classes:
AbstractFileLoader, AbstractLoader, ArffLoader, C45Loader, CSVLoader, DatabaseLoader, LibSVMLoader, SerializedInstancesLoader, TextDirectoryLoader, XRFFLoader

public interface Loader
extends java.io.Serializable

Interface to something that can load Instances from an input source in some format.

Version:
$Revision: 1.10 $
Author:
Mark Hall (mhall@cs.waikato.ac.nz)

Method Summary
 Instances getDataSet()
          Return the full data set.
 Instance getNextInstance(Instances structure)
          Read the data set incrementally---get the next instance in the data set or returns null if there are no more instances to get.
 Instances getStructure()
          Determines and returns (if possible) the structure (internally the header) of the data set as an empty set of instances.
 void reset()
          Resets the Loader object ready to begin loading.
 void setSource(java.io.File file)
          Resets the Loader object and sets the source of the data set to be the supplied File object.
 void setSource(java.io.InputStream input)
          Resets the Loader object and sets the source of the data set to be the supplied InputStream.
 

Method Detail

reset

void reset()
           throws java.lang.Exception
Resets the Loader object ready to begin loading. If there is an existing source, implementations should attempt to reset in such a fashion as to be able to load from the beginning of the source.

Throws:
java.lang.Exception - if Loader can't be reset for some reason.

setSource

void setSource(java.io.File file)
               throws java.io.IOException
Resets the Loader object and sets the source of the data set to be the supplied File object.

Parameters:
file - the File
Throws:
java.io.IOException - if an error occurs support loading from a File.

    public_normal_behavior
      requires: file != null
                && (* file exists *);
      modifiable: model_sourceSupplied, model_structureDetermined;
      ensures: model_sourceSupplied == true 
               && model_structureDetermined == false;
  also
    public_exceptional_behavior
      requires: file == null
                || (* file does not exist *);
    signals: (IOException);
 

setSource

void setSource(java.io.InputStream input)
               throws java.io.IOException
Resets the Loader object and sets the source of the data set to be the supplied InputStream.

Parameters:
input - the source InputStream
Throws:
java.io.IOException - if this Loader doesn't support loading from a File.

getStructure

Instances getStructure()
                       throws java.io.IOException
Determines and returns (if possible) the structure (internally the header) of the data set as an empty set of instances.

Returns:
the structure of the data set as an empty set of Instances
Throws:
java.io.IOException - if there is no source or parsing fails

    public_normal_behavior
      requires: model_sourceSupplied == true
                && model_structureDetermined == false
                && (* successful parse *);
      modifiable: model_structureDetermined;
      ensures: \result != null
               && \result.numInstances() == 0
               && model_structureDetermined == true;
  also
    public_exceptional_behavior
      requires: model_sourceSupplied == false
                || (* unsuccessful parse *);
      signals: (IOException);
 

getDataSet

Instances getDataSet()
                     throws java.io.IOException
Return the full data set. If the structure hasn't yet been determined by a call to getStructure then the method should do so before processing the rest of the data set.

Returns:
the full data set as an Instances object
Throws:
java.io.IOException - if there is an error during parsing or if getNextInstance has been called on this source (either incremental or batch loading can be used, not both).

    public_normal_behavior
      requires: model_sourceSupplied == true
                && (* successful parse *);
      modifiable: model_structureDetermined;
      ensures: \result != null
               && \result.numInstances() >= 0
               && model_structureDetermined == true;
  also
    public_exceptional_behavior
      requires: model_sourceSupplied == false
                || (* unsuccessful parse *);
      signals: (IOException);
 

getNextInstance

Instance getNextInstance(Instances structure)
                         throws java.io.IOException
Read the data set incrementally---get the next instance in the data set or returns null if there are no more instances to get. If the structure hasn't yet been determined by a call to getStructure then method should do so before returning the next instance in the data set. If it is not possible to read the data set incrementally (ie. in cases where the data set structure cannot be fully established before all instances have been seen) then an exception should be thrown.

Parameters:
structure - the dataset header information, will get updated in case of string or relational attributes
Returns:
the next instance in the data set as an Instance object or null if there are no more instances to be read
Throws:
java.io.IOException - if there is an error during parsing or if getDataSet has been called on this source (either incremental or batch loading can be used, not both).