feat(jcabi#277): first failed attempt to optimize the code

src/main/java/com/jcabi/xml/DomParser.java

@@ -31,8 +31,10 @@
 
 import com.jcabi.log.Logger;
 import java.io.ByteArrayInputStream;
+import java.io.File;
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
+import java.util.function.Function;
 import javax.xml.parsers.DocumentBuilder;
 import javax.xml.parsers.DocumentBuilderFactory;
 import javax.xml.parsers.ParserConfigurationException;
@@ -55,13 +57,15 @@ final class DomParser {
     /**
      * The XML as a text.
      */
-    private final transient byte[] xml;
+//    private final transient byte[] xml;
 
     /**
      * Document builder factory to use for parsing.
      */
     private final transient DocumentBuilderFactory factory;
 
+    private final Parser parser;
+
     /**
      * Public ctor.
      *
@@ -92,7 +96,33 @@ final class DomParser {
      */
     @SuppressWarnings("PMD.ArrayIsStoredDirectly")
     DomParser(final DocumentBuilderFactory fct, final byte[] bytes) {
-        this.xml = bytes;
+//        this.xml = bytes;
+        this.parser = new Parser() {
+            @Override
+            public Document apply(final DocumentBuilder builder) throws IOException, SAXException {
+                return builder.parse(new ByteArrayInputStream(bytes));
+            }
+
+            @Override
+            public long length() {
+                return bytes.length;
+            }
+        };
+        this.factory = fct;
+    }
+
+    DomParser(final  DocumentBuilderFactory fct, final File file){
+        this.parser = new Parser() {
+            @Override
+            public Document apply(final DocumentBuilder builder) throws IOException, SAXException {
+                return builder.parse(file);
+            }
+
+            @Override
+            public long length() {
+                return file.length();
+            }
+        };
         this.factory = fct;
     }
 
@@ -116,7 +146,8 @@ public Document document() {
         final long start = System.nanoTime();
         final Document doc;
         try {
-            doc = builder.parse(new ByteArrayInputStream(this.xml));
+//            doc = builder.parse(new ByteArrayInputStream(this.xml));
+            doc = this.parser.apply(builder);
         } catch (final IOException | SAXException ex) {
             throw new IllegalArgumentException(
                 String.format(
@@ -131,11 +162,18 @@ public Document document() {
                 this,
                 "%s parsed %d bytes of XML in %[nano]s",
                 builder.getClass().getName(),
-                this.xml.length,
+                this.parser.length(),
                 System.nanoTime() - start
             );
         }
         return doc;
     }
 
+    private interface Parser {
+
+        Document apply(DocumentBuilder builder) throws IOException, SAXException;
+
+        long length();
+    }
+
 }

src/main/java/com/jcabi/xml/XMLDocument.java

@@ -203,6 +203,7 @@ public XMLDocument(final Source source) {
      */
     public XMLDocument(final File file) throws FileNotFoundException {
         this(new TextResource(file).toString());
+//        this(new DomParser(XMLDocument.configuredDFactory(), file).document());
     }
 
     /**

src/test/java/com/jcabi/xml/XMLDocumentTest.java

@@ -719,7 +719,7 @@ void createsManyXmlDocuments() throws ParserConfigurationException, IOException,
     }
 
 
-   // ~ 1.6
+    // ~ 1.6
     @RepeatedTest(10)
     void createsXmlFromFile(
         @TempDir final Path temp
@@ -772,7 +772,7 @@ private String large() {
             "<credit>test-2</credit>",
             "</payment>"
         );
-        IntStream.range(0, 100).mapToObj(i -> payment).forEach(builder::append);
+        IntStream.range(0, 1_000).mapToObj(i -> payment).forEach(builder::append);
         return builder.append("</root>").toString();
     }