Java class< file using the Apache Tika< library is employed. For document type detection and content extraction from various file formats, it uses various document parsers and document type detection techniques to detect and extract data. It provides one generic API for parsing different file formats. of this parser, libraries are encapsulated during a single interface called the Parser interface.

Java supports multiple in-built classes and packages to extract and access the content from a PDF document. the subsequent classes are utilized in the extraction of the content :

BodyContentHandler is an in-built class that creates a handler for the text, which writes these XHTML body character events and stores them in an internal string buffer. It is inherited from the parent class ContentHandlerDecorator in Java. The specified text can be retrieved using the method ContentHandlerDecorator.toString() provided by the parent class. 

PDFParser Java provides an in-built package that provides a class PDFParser, which parses the contents of PDF documents. It extracts the contents of a PDF Document stored within paragraphs, strings, and tables (without invoking tabular boundaries). It can be used to parse encrypted documents too if the password is specified as an argument. 

ParseContext: This class is a component of the Java package org.apache.tika.parser, which is used to parse context and pass it on to the Tika parsers.

Procedure:

1. Create a content handler.
2. Create a PDF file at the local directory within the system.
3. Now, create a FileInputStream having an equivalent path as that of the above PDF file created.
4. Create a content parser employing a metadata type object for the PDF document.
5. PDF document is now parsed using the PDF parser class.
6. Print the content of the PDF document as created above for instance the extraction of content within the above PDF.

Implementation: The following Java program is used to illustrate the extraction of content from the PDF document.

// Java Program to Extract Content from a PDF

// Importing java input/output classes
import java.io.File;
import java.io.FileInputStream;
// Imporing Apache POI classes
import org.apache.tika.metadata.Metadata;
import org.apache.tika.parser.ParseContext;
import org.apache.tika.parser.pdf.PDFParser;
import org.apache.tika.sax.BodyContentHandler;

// Class
public class GFG {

	// Main driver method
	public static void main(String[] args) throws Exception
	{

		// Create a content handler
		BodyContentHandler contenthandler
			= new BodyContentHandler();

		// Create a file in local directory
		File f = new File("C:/extractcontent.pdf");

		// Create a file input stream
		// on specified path with the created file
		FileInputStream fstream = new FileInputStream(f);

		// Create an object of type Metadata to use
		Metadata data = new Metadata();

		// Create a context parser for the pdf document
		ParseContext context = new ParseContext();

		// PDF document can be parsed using the PDFparser
		// class
		PDFParser pdfparser = new PDFParser();

		// Method parse invoked on PDFParser class
		pdfparser.parse(fstream, contenthandler, data,
						context);

		// Printing the contents of the pdf document
		// using toString() method in java
		System.out.println("Extracting contents :"
						+ contenthandler.toString());
	}
}