AbstractLoader

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## weka.core.converters
Class AbstractLoader

    java.lang.Object
      weka.core.converters.AbstractLoader

All Implemented Interfaces:
  java.io.Serializable, Loader, RevisionHandler

Direct Known Subclasses:
  AbstractFileLoader, DatabaseLoader, TextDirectoryLoader

    public abstract class AbstractLoader

extends java.lang.Object
implements Loader

Abstract class gives default implementation of setSource methods. All other methods must be overridden.

Version:
  $Revision: 1.9 $
Author:
  Richard Kirkby (rkirkby@cs.waikato.ac.nz)
See Also:
  Serialized Form

Constructor Summary
`AbstractLoader()`

Method Summary
`abstract Instances` | `getDataSet()` Return the full data set.
`abstract 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.
`abstract Instances` | `getStructure()` Determines and returns (if possible) the structure (internally the header) of the data set as an empty set of instances.
`void` | `reset()` Default implementation sets retrieval mode to NONE
`void` | `setSource(java.io.File file)` Default implementation throws an IOException.
`void` | `setSource(java.io.InputStream input)` Default implementation throws an IOException.

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Methods inherited from interface weka.core.RevisionHandler
`getRevision`

Constructor Detail

### AbstractLoader

    public AbstractLoader()

Method Detail

### setSource

    public void setSource(java.io.File file)
                   throws java.io.IOException

  Default implementation throws an IOException.

  Specified by:
    `setSource` in interface `Loader`
  Parameters:
    `file` - the File
  Throws:
    `java.io.IOException` - always

### reset

    public void reset()
               throws java.lang.Exception

  Default implementation sets retrieval mode to NONE

  Specified by:
    `reset` in interface `Loader`
  Throws:
    `never.`
    `java.lang.Exception` - if Loader can't be reset for some reason.

### setSource

    public void setSource(java.io.InputStream input)
                   throws java.io.IOException

  Default implementation throws an IOException.

  Specified by:
    `setSource` in interface `Loader`
  Parameters:
    `input` - the input stream
  Throws:
    `java.io.IOException` - always

### getStructure

    public abstract Instances getStructure()
                                    throws java.io.IOException

  Description copied from interface: `Loader`
  Determines and returns (if possible) the structure (internally the header) of the data set as an empty set of instances.

  Specified by:
    `getStructure` in interface `Loader`
  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

    public abstract Instances getDataSet()
                                  throws java.io.IOException

  Description copied from interface: `Loader`
  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.

  Specified by:
    `getDataSet` in interface `Loader`
  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

    public abstract Instance getNextInstance(Instances structure)
                                      throws java.io.IOException

  Description copied from interface: `Loader`
  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.

  Specified by:
    `getNextInstance` in interface `Loader`
  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).

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