DuplicateStatementFinder.java

package net.fortytwo.sesametools.deduplication;

import info.aduna.iteration.CloseableIteration;
import org.openrdf.model.Resource;
import org.openrdf.model.Statement;
import org.openrdf.model.ValueFactory;
import org.openrdf.model.impl.SimpleValueFactory;
import org.openrdf.sail.SailConnection;
import org.openrdf.sail.SailException;

import java.util.HashSet;
import java.util.Set;

/**
 * @author Joshua Shinavier (http://fortytwo.net)
 */
public class DuplicateStatementFinder {
    private static final ValueFactory valueFactory = SimpleValueFactory.getInstance();
    
    private DuplicateStatementFinder() {
        
    }

    public static Set<Statement> findDuplicateStatements(final SailConnection sc) throws SailException {
        boolean includeInferred = false;

        // The HashSet is safe because none of the statements we'll add have a
        // non-null named analysis context.
        Set<Statement> results = new HashSet<>();

        try (CloseableIteration<? extends Resource, SailException> contexts = sc.getContextIDs()) {
            while (contexts.hasNext()) {
                Resource ctx = contexts.next();
                if (null != ctx) {

                    try (CloseableIteration<? extends Statement, SailException> stmts
                                 = sc.getStatements(null, null, null, includeInferred, ctx)) {
                        while (stmts.hasNext()) {
                            Statement st = stmts.next();

                            try (CloseableIteration<? extends Statement, SailException> dups = sc.getStatements(
                                    st.getSubject(), st.getPredicate(), st.getObject(), includeInferred)) {
                                int count = 0;
                                while (dups.hasNext()) {
                                    count++;
                                    if (2 == count) {
                                        Statement dup = valueFactory.createStatement(
                                                st.getSubject(), st.getPredicate(), st.getObject());
                                        results.add(dup);
                                        break;
                                    }

                                    dups.next();
                                }
                            }
                        }
                    }
                }
            }
        }

        return results;
    }
}