https://lucene.apache.org/lucene-parent/lucene-core: Apache Lucene Java Core (The Apache Software Foundation) 
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The logical representation of a Document for indexing and searching. 
The document package provides the user level logical representation of content to be indexed and searched. The package also provides utilities for working with Documents and IndexableFields.


Document and IndexableField


A Document is a collection of IndexableFields. A IndexableField is a logical representation of a user's content that needs to be indexed or stored. IndexableFields have a number of properties that tell Lucene how to treat the content (like indexed, tokenized, stored, etc.) See the Field implementation of IndexableField for specifics on these properties. 


Note: it is common to refer to Documents having Fields, even though technically they have IndexableFields.


Working with Documents


First and foremost, a Document is something created by the user application. It is your job to create Documents based on the content of the files you are working with in your application (Word, txt, PDF, Excel or any other format.) How this is done is completely up to you. That being said, there are many tools available in other projects that can make the process of taking a file and converting it into a Lucene Document. 


The DateTools is a utility class to make dates and times searchable. IntPoint, LongPoint, FloatPoint and DoublePoint enable indexing of numeric values (and also dates) for fast range queries using PointRangeQuery


/** 
 * The logical representation of a {@link org.apache.lucene.document.Document} for indexing and searching.
 * <p>The document package provides the user level logical representation of content to be indexed and searched.  The
 * package also provides utilities for working with {@link org.apache.lucene.document.Document}s and {@link org.apache.lucene.index.IndexableField}s.</p>
 * <h2>Document and IndexableField</h2>
 * <p>A {@link org.apache.lucene.document.Document} is a collection of {@link org.apache.lucene.index.IndexableField}s.  A
 *   {@link org.apache.lucene.index.IndexableField} is a logical representation of a user's content that needs to be indexed or stored.
 *   {@link org.apache.lucene.index.IndexableField}s have a number of properties that tell Lucene how to treat the content (like indexed, tokenized,
 *   stored, etc.)  See the {@link org.apache.lucene.document.Field} implementation of {@link org.apache.lucene.index.IndexableField}
 *   for specifics on these properties.
 * </p>
 * <p>Note: it is common to refer to {@link org.apache.lucene.document.Document}s having {@link org.apache.lucene.document.Field}s, even though technically they have
 * {@link org.apache.lucene.index.IndexableField}s.</p>
 * <h2>Working with Documents</h2>
 * <p>First and foremost, a {@link org.apache.lucene.document.Document} is something created by the user application.  It is your job
 *   to create Documents based on the content of the files you are working with in your application (Word, txt, PDF, Excel or any other format.)
 *   How this is done is completely up to you.  That being said, there are many tools available in other projects that can make
 *   the process of taking a file and converting it into a Lucene {@link org.apache.lucene.document.Document}.
 * </p>
 * <p>The {@link org.apache.lucene.document.DateTools} is a utility class to make dates and times searchable. {@link
 * org.apache.lucene.document.IntPoint}, {@link org.apache.lucene.document.LongPoint},
 * {@link org.apache.lucene.document.FloatPoint} and {@link org.apache.lucene.document.DoublePoint} enable indexing
 * of numeric values (and also dates) for fast range queries using {@link org.apache.lucene.search.PointRangeQuery}</p>
 */
package org.apache.lucene.document;