code cleanup

compliance/sparql/src/test/java/org/eclipse/rdf4j/query/parser/sparql/SPARQLServiceEvaluationTest.java

@@ -268,7 +268,7 @@ public void testVariableNameHandling() throws Exception {
 			assertTrue(tqr.hasNext());
 
 			List<BindingSet> result = QueryResults.asList(tqr);
-			assertTrue(result.size() > 0);
+			assertTrue(!result.isEmpty());
 			for (BindingSet bs : result) {
 				assertTrue(bs.hasBinding("val"));
 				assertTrue(bs.hasBinding("s"));

core/common/io/src/main/java/org/eclipse/rdf4j/common/net/ParsedIRI.java

@@ -355,7 +355,7 @@ public String toASCIIString() {
 				appendAscii(sb, userInfo);
 				sb.append('@');
 			}
-			if (host.length() > 0) {
+			if (!host.isEmpty()) {
 				sb.append(IDN.toASCII(host, IDN.ALLOW_UNASSIGNED));
 			}
 			if (port >= 0) {
@@ -516,7 +516,7 @@ public ParsedIRI normalize() {
 		boolean localhost = isScheme("file") && userInfo == null && -1 == port
 				&& ("".equals(host) || "localhost".equals(host));
 		String _host = localhost ? null
-				: host == null || host.length() == 0 ? host
+				: host == null || host.isEmpty() ? host
 						: IDN.toUnicode(pctEncodingNormalization(toLowerCase(host)),
 								IDN.USE_STD3_ASCII_RULES | IDN.ALLOW_UNASSIGNED);
 		String _path = _scheme != null && path == null ? "" : normalizePath(path);
@@ -581,14 +581,14 @@ public ParsedIRI resolve(ParsedIRI relative) {
 		// relURI._scheme == null
 
 		// RFC, step 2:
-		if (relative.getHost() == null && relative.getQuery() == null && relative.getPath().length() == 0) {
+		if (relative.getHost() == null && relative.getQuery() == null && relative.getPath().isEmpty()) {
 
 			// Inherit any fragment identifier from relURI
 			String fragment = relative.getFragment();
 
 			return new ParsedIRI(this.getScheme(), this.getUserInfo(), this.getHost(), this.getPort(), this.getPath(),
 					this.getQuery(), fragment);
-		} else if (relative.getHost() == null && relative.getPath().length() == 0) {
+		} else if (relative.getHost() == null && relative.getPath().isEmpty()) {
 
 			// Inherit any query or fragment from relURI
 			String query = relative.getQuery();
@@ -636,7 +636,7 @@ public ParsedIRI resolve(ParsedIRI relative) {
 						path = path.substring(0, lastSlashIdx + 1);
 					}
 
-					if (path.length() == 0) {
+					if (path.isEmpty()) {
 						// No path means: start at root.
 						path = "/";
 					}
@@ -782,7 +782,7 @@ private void parse() throws URISyntaxException {
 			if (':' == peek()) {
 				advance(1);
 				String p = parseMember(DIGIT, '/');
-				if (p.length() > 0) {
+				if (!p.isEmpty()) {
 					port = Integer.parseInt(p);
 				} else {
 					port = -1;
@@ -1101,7 +1101,7 @@ && isMember(ALPHA, path.codePointAt(1))) {
 	}
 
 	private String pctEncodingNormalization(String path) {
-		if (path == null || path.length() == 0 || path.indexOf('%') < 0) {
+		if (path == null || path.isEmpty() || path.indexOf('%') < 0) {
 			return path; // no pct encodings
 		}
 		String[] encodings = listPctEncodings(path);

core/http/client/src/main/java/org/eclipse/rdf4j/http/client/RDF4JProtocolSession.java

@@ -1069,7 +1069,7 @@ protected void upload(HttpEntity reqEntity, String baseURI, boolean overwrite, b
 			for (String encodedContext : Protocol.encodeContexts(contexts)) {
 				url.addParameter(Protocol.CONTEXT_PARAM_NAME, encodedContext);
 			}
-			if (baseURI != null && baseURI.trim().length() != 0) {
+			if (baseURI != null && !baseURI.trim().isEmpty()) {
 				String encodedBaseURI = Protocol.encodeValue(SimpleValueFactory.getInstance().createIRI(baseURI));
 				url.setParameter(Protocol.BASEURI_PARAM_NAME, encodedBaseURI);
 			}

core/http/client/src/main/java/org/eclipse/rdf4j/http/client/SPARQLProtocolSession.java

@@ -606,7 +606,7 @@ protected List<NameValuePair> getUpdateMethodParameters(QueryLanguage ql, String
 		}
 
 		if (dataset != null) {
-			if (dataset.getDefaultRemoveGraphs().size() > 0) {
+			if (!dataset.getDefaultRemoveGraphs().isEmpty()) {
 				if (!(dataset.getDefaultRemoveGraphs().equals(dataset.getDefaultGraphs()))) {
 					logger.warn(
 							"ambiguous dataset spec for SPARQL endpoint: default graphs and default remove graphs both defined but not equal");
@@ -1091,7 +1091,7 @@ protected HttpResponse execute(HttpUriRequest method) throws IOException, RDF4JE
 						throw new RepositoryException(new RemoteShaclValidationException(
 								new StringReader(errInfo.toString()), "", format));
 
-					} else if (errInfo.toString().length() > 0) {
+					} else if (!errInfo.toString().isEmpty()) {
 						throw new RepositoryException(errInfo.toString());
 					} else {
 						throw new RepositoryException(response.getStatusLine().getReasonPhrase());

core/http/client/src/main/java/org/eclipse/rdf4j/http/client/query/AbstractHTTPQuery.java

@@ -44,7 +44,7 @@ protected AbstractHTTPQuery(SPARQLProtocolSession httpClient, QueryLanguage quer
 		// for legacy reasons we should support the empty string for baseURI
 		// this is used in the SPARQL repository in several places, e.g. in
 		// getStatements
-		this.baseURI = baseURI != null && baseURI.length() > 0 ? baseURI : null;
+		this.baseURI = baseURI != null && !baseURI.isEmpty() ? baseURI : null;
 	}
 
 	/**

core/model/src/main/java/org/eclipse/rdf4j/model/datatypes/XMLDatatypeUtil.java

@@ -2100,7 +2100,7 @@ public static Duration parseDuration(String s) {
 	 * plus signs cannot be parsed by methods such as {@link Integer#parseInt(String)}.
 	 */
 	private static String trimPlusSign(String s) {
-		if (s.length() > 0 && s.charAt(0) == '+') {
+		if (!s.isEmpty() && s.charAt(0) == '+') {
 			return s.substring(1);
 		} else {
 			return s;

core/model/src/main/java/org/eclipse/rdf4j/model/impl/ValidatingValueFactory.java

@@ -94,7 +94,7 @@ public IRI createIRI(String namespace, String localName) {
 
 	@Override
 	public BNode createBNode(String nodeID) {
-		if (nodeID.length() < 1) {
+		if (nodeID.isEmpty()) {
 			throw new IllegalArgumentException("Blank node ID cannot be empty");
 		}
 		if (!isMember(PN_CHARS_U, nodeID.codePointAt(0))) {

core/model/src/main/java/org/eclipse/rdf4j/model/util/Literals.java

@@ -545,7 +545,7 @@ public static boolean isValidLanguageTag(String languageTag) {
 	public static boolean langMatches(String langTag, String langRange) {
 		boolean result = false;
 		if (langRange.equals("*")) {
-			result = langTag.length() > 0;
+			result = !langTag.isEmpty();
 		} else if (langTag.length() == langRange.length()) {
 			result = langTag.equalsIgnoreCase(langRange);
 		} else if (langTag.length() > langRange.length()) {

core/model/src/main/java/org/eclipse/rdf4j/model/util/URIUtil.java

@@ -97,7 +97,7 @@ public static boolean isCorrectURISplit(String namespace, String localName) {
 		assert namespace != null : "namespace must not be null";
 		assert localName != null : "localName must not be null";
 
-		if (namespace.length() == 0) {
+		if (namespace.isEmpty()) {
 			return false;
 		}
 
@@ -213,7 +213,7 @@ private static boolean isUnreserved(char c) {
 	 */
 	public static boolean isValidLocalName(String name) {
 		// Empty names are legal
-		if (name.length() == 0) {
+		if (name.isEmpty()) {
 			return true;
 		}
 

core/query/src/main/java/org/eclipse/rdf4j/query/impl/EmptyBindingSet.java

@@ -69,7 +69,7 @@ public int size() {
 	@Override
 	public boolean equals(Object o) {
 		if (o instanceof BindingSet) {
-			return ((BindingSet) o).size() == 0;
+			return ((BindingSet) o).isEmpty();
 		}
 
 		return false;

core/queryalgebra/evaluation/src/main/java/org/eclipse/rdf4j/query/algebra/evaluation/impl/QueryEvaluationContext.java

@@ -61,20 +61,21 @@ class Minimal implements QueryEvaluationContext {
 		// this field is volatile, as a precaution in case we call it directly.
 		private volatile Literal now;
 		private final Dataset dataset;
-		private final ValueFactory vf;
+		private final ValueFactory valueFactory;
 		private final Comparator<Value> comparator;
 
 		/**
 		 * Set the shared now value to a preexisting object
 		 *
-		 * @param now     that is shared.
-		 * @param dataset that a query should use to evaluate
+		 * @param now        that is shared.
+		 * @param dataset    that a query should use to evaluate
+		 * @param comparator to use for ordering
 		 */
 		public Minimal(Literal now, Dataset dataset, Comparator<Value> comparator) {
 			super();
 			this.now = now;
 			this.dataset = dataset;
-			this.vf = SimpleValueFactory.getInstance();
+			this.valueFactory = SimpleValueFactory.getInstance();
 			this.comparator = comparator;
 		}
 
@@ -85,47 +86,42 @@ public Minimal(Literal now, Dataset dataset, Comparator<Value> comparator) {
 		 * @param dataset that a query should use to evaluate
 		 */
 		public Minimal(Literal now, Dataset dataset) {
-			super();
-			this.now = now;
-			this.dataset = dataset;
-			this.vf = SimpleValueFactory.getInstance();
-			this.comparator = null;
+			this(now, dataset, null);
 		}
 
 		/**
 		 * @param dataset that a query should use to evaluate
 		 */
 		public Minimal(Dataset dataset) {
-			this.dataset = dataset;
-			this.vf = SimpleValueFactory.getInstance();
-			this.comparator = null;
+			this(null, dataset);
 		}
 
 		/**
-		 * @param dataset that a query should use to evaluate
+		 * @param dataset    that a query should use to evaluate
+		 * @param comparator to use for ordering
 		 */
 		public Minimal(Dataset dataset, Comparator<Value> comparator) {
-			this.dataset = dataset;
-			this.vf = SimpleValueFactory.getInstance();
-			this.comparator = comparator;
+			this(null, dataset, comparator);
 		}
 
 		/**
-		 * @param dataset that a query should use to the evaluate
+		 * @param dataset      that a query should use to the evaluate
+		 * @param valueFactory that a query should use to the evaluate
+		 * @param comparator   to use for ordering
+		 *
 		 */
-		public Minimal(Dataset dataset, ValueFactory vf, Comparator<Value> comparator) {
+		public Minimal(Dataset dataset, ValueFactory valueFactory, Comparator<Value> comparator) {
 			this.dataset = dataset;
-			this.vf = vf;
+			this.valueFactory = valueFactory;
 			this.comparator = comparator;
 		}
 
 		/**
-		 * @param dataset that a query should use to the evaluate
+		 * @param dataset      that a query should use to the evaluate
+		 * @param valueFactory that a query should use to the evaluate
 		 */
-		public Minimal(Dataset dataset, ValueFactory vf) {
-			this.dataset = dataset;
-			this.vf = vf;
-			this.comparator = null;
+		public Minimal(Dataset dataset, ValueFactory valueFactory) {
+			this(dataset, valueFactory, null);
 		}
 
 		@Override
@@ -140,7 +136,7 @@ public Literal getNow() {
 			// creating a new date is expensive because it uses the XMLGregorianCalendar implementation which is very
 			// complex.
 			if (now == null) {
-				now = vf.createLiteral(new Date());
+				now = valueFactory.createLiteral(new Date());
 				boolean success = NOW.compareAndSet(this, null, now);
 				if (!success) {
 					now = (Literal) NOW.getAcquire(this);

core/queryalgebra/evaluation/src/main/java/org/eclipse/rdf4j/query/algebra/evaluation/impl/evaluationsteps/BindingSetAssignmentQueryEvaluationStep.java

@@ -36,7 +36,7 @@ public BindingSetAssignmentQueryEvaluationStep(BindingSetAssignment node, QueryE
 	@Override
 	public CloseableIteration<BindingSet> evaluate(BindingSet bindings) {
 		final Iterator<BindingSet> assignments = node.getBindingSets().iterator();
-		if (bindings.size() == 0) {
+		if (bindings.isEmpty()) {
 			// we can just return the assignments directly without checking existing bindings
 			return new CloseableIteratorIteration<>(assignments);
 		}

core/queryalgebra/evaluation/src/main/java/org/eclipse/rdf4j/query/algebra/evaluation/optimizer/BindingAssignerOptimizer.java

@@ -28,7 +28,7 @@ public class BindingAssignerOptimizer implements QueryOptimizer {
 
 	@Override
 	public void optimize(TupleExpr tupleExpr, Dataset dataset, BindingSet bindings) {
-		if (bindings.size() > 0) {
+		if (!bindings.isEmpty()) {
 			tupleExpr.visit(new VarVisitor(bindings));
 		}
 	}

core/queryalgebra/evaluation/src/main/java/org/eclipse/rdf4j/query/algebra/evaluation/util/QueryEvaluationUtil.java

@@ -68,7 +68,7 @@ public static boolean getEffectiveBooleanValue(Value value) throws ValueExprEval
 			CoreDatatype.XSD datatype = literal.getCoreDatatype().asXSDDatatypeOrNull();
 
 			if (datatype == CoreDatatype.XSD.STRING) {
-				return label.length() > 0;
+				return !label.isEmpty();
 			} else if (datatype == CoreDatatype.XSD.BOOLEAN) {
 				// also false for illegal values
 				return "true".equals(label) || "1".equals(label);

core/queryalgebra/evaluation/src/main/java/org/eclipse/rdf4j/query/algebra/evaluation/util/QueryEvaluationUtility.java

@@ -59,7 +59,7 @@ public static Result getEffectiveBooleanValue(Value value) {
 			CoreDatatype.XSD datatype = literal.getCoreDatatype().asXSDDatatypeOrNull();
 
 			if (datatype == CoreDatatype.XSD.STRING) {
-				return Result.fromBoolean(label.length() > 0);
+				return Result.fromBoolean(!label.isEmpty());
 			} else if (datatype == CoreDatatype.XSD.BOOLEAN) {
 				// also false for illegal values
 				return Result.fromBoolean("true".equals(label) || "1".equals(label));

core/queryalgebra/model/src/main/java/org/eclipse/rdf4j/query/algebra/Join.java

@@ -13,6 +13,8 @@
 import java.util.LinkedHashSet;
 import java.util.Set;
 
+import org.eclipse.rdf4j.common.annotation.Experimental;
+
 /**
  * A natural join between two tuple expressions.
  */
@@ -72,14 +74,17 @@ public Join clone() {
 		return (Join) super.clone();
 	}
 
+	@Experimental
 	public boolean isMergeJoin() {
 		return mergeJoin;
 	}
 
+	@Experimental
 	public void setMergeJoin(boolean mergeJoin) {
 		this.mergeJoin = mergeJoin;
 	}
 
+	@Experimental
 	public void setCacheable(boolean cacheable) {
 		this.cacheable = cacheable;
 	}

core/queryalgebra/model/src/main/java/org/eclipse/rdf4j/query/algebra/MultiProjection.java

@@ -86,7 +86,7 @@ public Set<String> getBindingNames() {
 	public Set<String> getAssuredBindingNames() {
 		Set<String> bindingNames = new HashSet<>();
 
-		if (projections.size() >= 1) {
+		if (!projections.isEmpty()) {
 			Set<String> assuredSourceNames = getArg().getAssuredBindingNames();
 
 			bindingNames.addAll(projections.get(0).getProjectedNamesFor(assuredSourceNames));

core/queryparser/api/src/main/java/org/eclipse/rdf4j/query/impl/AbstractParserUpdate.java

@@ -88,11 +88,11 @@ protected Dataset getMergedDataset(Dataset sparqlDefinedDataset) {
 
 		// if there are default graphs in the SPARQL update but it's not a WITH
 		// clause, it's a USING clause
-		final boolean hasUsingClause = !hasWithClause && sparqlDefaultGraphs != null ? sparqlDefaultGraphs.size() > 0
+		final boolean hasUsingClause = !hasWithClause && sparqlDefaultGraphs != null ? !sparqlDefaultGraphs.isEmpty()
 				: false;
 
 		final Set<IRI> sparqlNamedGraphs = sparqlDefinedDataset.getNamedGraphs();
-		final boolean hasUsingNamedClause = sparqlNamedGraphs != null ? sparqlNamedGraphs.size() > 0 : false;
+		final boolean hasUsingNamedClause = sparqlNamedGraphs != null ? !sparqlNamedGraphs.isEmpty() : false;
 
 		if (hasUsingClause) {
 			// one or more USING-clauses in the update itself, we need to

core/queryparser/api/src/main/java/org/eclipse/rdf4j/query/parser/impl/AbstractParserUpdate.java

@@ -90,11 +90,11 @@ protected Dataset getMergedDataset(Dataset sparqlDefinedDataset) {
 
 		// if there are default graphs in the SPARQL update but it's not a WITH
 		// clause, it's a USING clause
-		final boolean hasUsingClause = !hasWithClause && sparqlDefaultGraphs != null ? sparqlDefaultGraphs.size() > 0
+		final boolean hasUsingClause = !hasWithClause && sparqlDefaultGraphs != null ? !sparqlDefaultGraphs.isEmpty()
 				: false;
 
 		final Set<IRI> sparqlNamedGraphs = sparqlDefinedDataset.getNamedGraphs();
-		final boolean hasUsingNamedClause = sparqlNamedGraphs != null ? sparqlNamedGraphs.size() > 0 : false;
+		final boolean hasUsingNamedClause = sparqlNamedGraphs != null ? !sparqlNamedGraphs.isEmpty() : false;
 
 		if (hasUsingClause) {
 			// one or more USING-clauses in the update itself, we need to

core/queryparser/sparql/src/main/java/org/eclipse/rdf4j/query/parser/sparql/SPARQLParser.java

@@ -259,7 +259,7 @@ public static void main(String[] args) throws java.io.IOException {
 
 		int emptyLineCount = 0;
 		while ((line = in.readLine()) != null) {
-			if (line.length() > 0) {
+			if (!line.isEmpty()) {
 				emptyLineCount = 0;
 				buf.append(' ').append(line).append('\n');
 			} else {
@@ -269,7 +269,7 @@ public static void main(String[] args) throws java.io.IOException {
 			if (emptyLineCount == 2) {
 				emptyLineCount = 0;
 				String queryStr = buf.toString().trim();
-				if (queryStr.length() > 0) {
+				if (!queryStr.isEmpty()) {
 					try {
 						long start = System.currentTimeMillis();
 						ParsedOperation parsedQuery = QueryParserUtil.parseOperation(QueryLanguage.SPARQL, queryStr,

core/queryparser/sparql/src/main/java/org/eclipse/rdf4j/query/parser/sparql/TupleExprBuilder.java

@@ -561,7 +561,7 @@ public TupleExpr visit(ASTSelect node, Object data) throws VisitorException {
 				AggregateCollector collector = new AggregateCollector();
 				valueExpr.visit(collector);
 
-				if (collector.getOperators().size() > 0) {
+				if (!collector.getOperators().isEmpty()) {
 					elem.setAggregateOperatorInExpression(true);
 					for (AggregateOperator operator : collector.getOperators()) {
 						// Apply implicit grouping if necessary
@@ -1150,7 +1150,7 @@ public String visit(ASTGroupCondition node, Object data) throws VisitorException
 			extension.addElement(elem);
 		}
 
-		if (extension.getElements().size() > 0 && !(arg instanceof Extension)) {
+		if (!extension.getElements().isEmpty() && !(arg instanceof Extension)) {
 			extension.setArg(arg);
 			group.setArg(extension);
 		}