Consolidate spreadsheet PictureData javadocs

If docs for an implementation were identical or substantially similar to that of the interface, I removed them from the implementation, as Javadocs inherit automatically.

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1893780 13f79535-47bb-0310-9956-ffa450edef68

poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFPictureData.java

@@ -93,26 +93,12 @@ public class XSSFPictureData extends POIXMLDocumentPart implements PictureData {
         }
     }
 
-    /**
-     * Suggests a file extension for this image.
-     *
-     * @return the file extension.
-     */
+    @Override
     public String suggestFileExtension() {
         return getPackagePart().getPartName().getExtension();
     }
 
-    /**
-     * Return an integer constant that specifies type of this picture
-     *
-     * @return an integer constant that specifies type of this picture 
-     * @see org.apache.poi.ss.usermodel.Workbook#PICTURE_TYPE_EMF
-     * @see org.apache.poi.ss.usermodel.Workbook#PICTURE_TYPE_WMF
-     * @see org.apache.poi.ss.usermodel.Workbook#PICTURE_TYPE_PICT
-     * @see org.apache.poi.ss.usermodel.Workbook#PICTURE_TYPE_JPEG
-     * @see org.apache.poi.ss.usermodel.Workbook#PICTURE_TYPE_PNG
-     * @see org.apache.poi.ss.usermodel.Workbook#PICTURE_TYPE_DIB
-     */
+    @Override
     public int getPictureType(){
         String contentType = getPackagePart().getContentType();
         for (int i = 0; i < RELATIONS.length; i++) {

poi/src/main/java/org/apache/poi/hssf/usermodel/HSSFPictureData.java

@@ -102,9 +102,6 @@ public class HSSFPictureData implements PictureData
         }
     }
 
-    /**
-     * Returns the mime type for the image
-     */
     @Override
     public String getMimeType() {
        switch (EscherRecordTypes.forTypeID(blip.getRecordId())) {
@@ -130,13 +127,6 @@ public class HSSFPictureData implements PictureData
     /**
      * @return the POI internal image type, 0 if unknown image type (was -1 prior to 5.0.0 but
      * that was inconsistent with other {@link PictureData} implementations)
-     *
-     * @see Workbook#PICTURE_TYPE_DIB
-     * @see Workbook#PICTURE_TYPE_EMF
-     * @see Workbook#PICTURE_TYPE_JPEG
-     * @see Workbook#PICTURE_TYPE_PICT
-     * @see Workbook#PICTURE_TYPE_PNG
-     * @see Workbook#PICTURE_TYPE_WMF
      */
     @Override
     public int getPictureType() {

poi/src/main/java/org/apache/poi/ss/usermodel/PictureData.java

@@ -29,7 +29,8 @@ public interface PictureData {
     /**
      * Suggests a file extension for this image.
      *
-     * @return the file extension.
+     * @return the file extension, without a leading {@code .}. Never {@code null}, but will be empty if the extension
+     * is unknown or if the file backing these data does not have an extension.
      */
     String suggestFileExtension();
 
@@ -39,7 +40,7 @@ public interface PictureData {
     String getMimeType();
     
     /**
-     * @return the POI internal image type, 0 if unknown image type
+     * @return the POI internal image type, {@code 0} if unknown image type
      *
      * @see Workbook#PICTURE_TYPE_DIB
      * @see Workbook#PICTURE_TYPE_EMF