How to run dql search query in java?

I want to check whether a file is present in a particular folder in documentum using Java.

Following is my code,

import com.documentum.com.DfClientX;
import com.documentum.com.IDfClientX;
import com.documentum.fc.client.DfQuery;
import com.documentum.fc.client.IDfClient;
import com.documentum.fc.client.IDfCollection;
import com.documentum.fc.client.IDfFolder;
import com.documentum.fc.client.IDfQuery;
import com.documentum.fc.client.IDfSession;
import com.documentum.fc.client.IDfSessionManager;
import com.documentum.fc.common.DfException;
import com.documentum.fc.common.DfId;
import com.documentum.fc.common.IDfLoginInfo;
import com.documentum.operations.IDfDeleteOperation;

public class CountFiles {

    // Documentum target repository where the files will be imported
    private static final String REPO_NAME = "rep";



    public static void main( String[] args ) throws Exception {

        try {
            String username = "user";
            String password = "pwd";

            System.out.println( "Starting to connect ..." );

            IDfSessionManager sessMgr = createSessionManager( );
            addIdentity( sessMgr, username, password);
            IDfSession sess = sessMgr.getSession(REPO_NAME );
            System.out.println( "Successfully connected to the server.");
            queryDocumentum(sess);


        } catch( Exception ex ) {
            System.out.println( ex );
            ex.printStackTrace( );
        }
    }


    private static void queryDocumentum(IDfSession sess) throws DfException {
    IDfQuery query = new DfQuery();
String queryStr= "select count(*) from dm_document WHERE FOLDER ('/XXX/YYY',DESCEND) search document contains 'abc.pdf' ";
    query.setDQL(queryStr);
    IDfCollection coll = query.execute(sess,IDfQuery.DF_EXEC_QUERY);
    while(coll.next())
    {
      System.out.println("Result of method: " + coll.getValueAt(0));
    }
    coll.close();
}
/**
     * Creates a new session manager instance. The session manager does not have
     * any identities associated with it.
     *
     * @return a new session manager object.
     * @throws DfException
     */
    private static IDfSessionManager createSessionManager( ) 
            throws Exception {
        IDfClientX clientX = new DfClientX( );
        IDfClient localClient = clientX.getLocalClient( );
        IDfSessionManager sessMgr = localClient.newSessionManager( );

        System.out.println( "Created session manager." );

        return sessMgr;
    }

    /**
     * Adds a new identity to the session manager.
     *
     */
    private static void addIdentity( final IDfSessionManager sm, 
            final String username, final String password ) 
            throws Exception {
        IDfClientX clientX = new DfClientX( );

        IDfLoginInfo li = clientX.getLoginInfo( );
        li.setUser( username );
        li.setPassword( password );

        // check if session manager already has an identity.
        // if yes, remove it.
        if( sm.hasIdentity( REPO_NAME ) ) {
            sm.clearIdentity( REPO_NAME );

            System.out.println( "Cleared identity on :" + REPO_NAME );
        }

        sm.setIdentity( REPO_NAME, li );

        System.out.println( "Set up identity for the user." );
    }

}

I am getting the following exception - [DM_QUERY_E_SYNTAX]error: "A Parser Error (syntax error) has occurred in the vicinity of "select count(*) from dm_document WHERE FOLDER ('/XXX/YYY',DESCEND) search document contains 'abc.pdf'". what is the issue in the query/code?

Well, obviously your DQL query is wrong:

select count(*) from dm_document WHERE FOLDER ('/XXX/YYY',DESCEND) search document contains 'abc.pdf'

if you just want to check if some document named 'abc.pdf' is present in path /XXX/YYY and all folders below (keyword 'descend') then the DQL should be more like this, you don't need Full Text search capabilities for that:

select count(*) from dm_document where folder('/XXX/YYY', DESCEND) and object_name = 'abc.pdf'

If you don't know exact file name you can use "LIKE", for example:

select count(*) from dm_document where folder('/XXX/YYY', DESCEND) and object_name LIKE '%abc.pdf'