if (condition) then
 ... 
else
 ... 

   
      
      Sonoo Jaiswal
      2012
      400.00
   
   
   
      
      Balaswamy
      2008
      300.50
   
   
   
      
      Ajeet Kumar
      Sam Lee
      2013
      250.00
   
   
   
      
      Ajeet Kumar
      2014
      150.50
   

{
   if(not(doc("books.xml"))) then (
      
         books.xml does not exist
      
   )
   else ( 
      for $x in doc("books.xml")/books/book    
      where $x/price>30
      return $x/title
   )
}


Create a Java based XQuery executor program to read the books.xqy,
 passes it to the XQuery expression processor, and executes the expression. After that the result will be displayed. 
XQueryTester.java

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;

import javax.xml.xquery.XQConnection;
import javax.xml.xquery.XQDataSource;
import javax.xml.xquery.XQException;
import javax.xml.xquery.XQPreparedExpression;
import javax.xml.xquery.XQResultSequence;

import com.saxonica.xqj.SaxonXQDataSource;

public class XQueryTester {
   public static void main(String[] args){
      try {
         execute();
      }
      
      catch (FileNotFoundException e) {
         e.printStackTrace();
      }
      
      catch (XQException e) {
         e.printStackTrace();
      }
   }

   private static void execute() throws FileNotFoundException, XQException{
      InputStream inputStream = new FileInputStream(new File("books.xqy"));
      XQDataSource ds = new SaxonXQDataSource();
      XQConnection conn = ds.getConnection();
      XQPreparedExpression exp = conn.prepareExpression(inputStream);
      XQResultSequence result = exp.executeQuery();
       while (result.next()) {
         System.out.println(result.getItemAsString(null));
      }
   }    
}