diff --git a/src/main/java/org/jpeek/App.java b/src/main/java/org/jpeek/App.java
index 3d9e24b6..e9729c3e 100644
--- a/src/main/java/org/jpeek/App.java
+++ b/src/main/java/org/jpeek/App.java
@@ -70,16 +70,13 @@
  *  and in `MetricsTest`).
  *  Once they are resolved add it to reports list.
  */
-@SuppressWarnings
-    (
-        {
-            "PMD.AvoidDuplicateLiterals",
-            "PMD.NPathComplexity",
-            "PMD.CyclomaticComplexity",
-            "PMD.StdCyclomaticComplexity",
-            "PMD.ModifiedCyclomaticComplexity"
-        }
-    )
+@SuppressWarnings({
+    "PMD.AvoidDuplicateLiterals",
+    "PMD.NPathComplexity",
+    "PMD.CyclomaticComplexity",
+    "PMD.StdCyclomaticComplexity",
+    "PMD.ModifiedCyclomaticComplexity"
+})
 public final class App {
 
     /**
@@ -172,11 +169,12 @@ public void analyze() throws IOException {
         final XSL chain = new XSLChain(layers);
         this.save(skeleton.toString(), "skeleton.xml");
         final Collection<Report> reports = new LinkedList<>();
+        final Calculus xsl = new XslCalculus();
         if (this.params.containsKey("LCOM")) {
             reports.add(
                 new XslReport(
                     chain.transform(skeleton),
-                    "LCOM", this.params, 10.0d, -5.0d
+                    "LCOM", this.params, xsl, 10.0d, -5.0d
                 )
             );
         }
@@ -184,7 +182,7 @@ public void analyze() throws IOException {
             reports.add(
                 new XslReport(
                     chain.transform(skeleton),
-                    "CAMC", this.params
+                    "CAMC", this.params, xsl
                 )
             );
         }
@@ -192,7 +190,7 @@ public void analyze() throws IOException {
             reports.add(
                 new XslReport(
                     chain.transform(skeleton),
-                    "MMAC", this.params, 0.5d, 0.1d
+                    "MMAC", this.params, xsl, 0.5d, 0.1d
                 )
             );
         }
@@ -200,7 +198,7 @@ public void analyze() throws IOException {
             reports.add(
                 new XslReport(
                     chain.transform(skeleton),
-                    "LCOM5", this.params, 0.5d, -0.1d
+                    "LCOM5", this.params, xsl, 0.5d, -0.1d
                 )
             );
         }
@@ -208,7 +206,7 @@ public void analyze() throws IOException {
             reports.add(
                 new XslReport(
                     chain.transform(skeleton),
-                    "NHD"
+                    "NHD", xsl
                 )
             );
         }
@@ -216,7 +214,7 @@ public void analyze() throws IOException {
             reports.add(
                 new XslReport(
                     chain.transform(skeleton),
-                    "LCOM2", this.params
+                    "LCOM2", this.params, xsl
                 )
             );
         }
@@ -224,7 +222,7 @@ public void analyze() throws IOException {
             reports.add(
                 new XslReport(
                     chain.transform(skeleton),
-                    "LCOM3", this.params
+                    "LCOM3", this.params, xsl
                 )
             );
         }
@@ -232,7 +230,7 @@ public void analyze() throws IOException {
             reports.add(
                 new XslReport(
                     chain.transform(skeleton),
-                    "SCOM", this.params
+                    "SCOM", this.params, xsl
                 )
             );
         }
@@ -240,7 +238,7 @@ public void analyze() throws IOException {
             reports.add(
                 new XslReport(
                     chain.transform(skeleton),
-                    "OCC", this.params
+                    "OCC", this.params, xsl
                 )
             );
         }
@@ -248,7 +246,7 @@ public void analyze() throws IOException {
             reports.add(
                 new XslReport(
                     chain.transform(skeleton),
-                    "PCC"
+                    "PCC", xsl
                 )
             );
         }
@@ -256,7 +254,7 @@ public void analyze() throws IOException {
             reports.add(
                 new XslReport(
                     chain.transform(skeleton),
-                    "TCC"
+                    "TCC", xsl
                 )
             );
         }
@@ -264,7 +262,7 @@ public void analyze() throws IOException {
             reports.add(
                 new XslReport(
                     chain.transform(skeleton),
-                    "LCC"
+                    "LCC", xsl
                 )
             );
         }
@@ -272,7 +270,7 @@ public void analyze() throws IOException {
             reports.add(
                 new XslReport(
                     chain.transform(skeleton),
-                    "CCM"
+                    "CCM", xsl
                 )
             );
         }
@@ -280,7 +278,7 @@ public void analyze() throws IOException {
             reports.add(
                 new XslReport(
                     chain.transform(skeleton),
-                    "MWE"
+                    "MWE", xsl
                 )
             );
         }
diff --git a/src/main/java/org/jpeek/Calculus.java b/src/main/java/org/jpeek/Calculus.java
new file mode 100644
index 00000000..bc37e832
--- /dev/null
+++ b/src/main/java/org/jpeek/Calculus.java
@@ -0,0 +1,51 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017-2019 Yegor Bugayenko
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package org.jpeek;
+
+import com.jcabi.xml.XML;
+import java.io.IOException;
+import java.util.Map;
+
+/**
+ * Metrics calculus interface.
+ * @since 0.30.9
+ * @todo #390:30min We have a separate interface to calculate XML metrics.
+ *  We should continue to the goal defined in #296 where we should have a java
+ *  implementation to calculate metrics. The motivation is to be able to make
+ *  calculations impossible or too difficult to implement in xsl, like LCOM4.
+ */
+public interface Calculus {
+
+    /**
+     * Produces {@link XML} representing metrics values.
+     * @param metric Desired metric to calculate
+     * @param params Params
+     * @param skeleton Package input
+     * @return XML document giving metrics values for classes
+     * @throws IOException If fails
+     */
+    XML node(String metric, Map<String, Object> params, XML skeleton)
+        throws IOException;
+
+}
diff --git a/src/main/java/org/jpeek/Report.java b/src/main/java/org/jpeek/Report.java
index 0385812e..eff295f7 100644
--- a/src/main/java/org/jpeek/Report.java
+++ b/src/main/java/org/jpeek/Report.java
@@ -29,10 +29,6 @@
 /**
  * Report interface.
  * @since 0.1
- * @todo #296:30min Now that we have the infrastructure to implement
- *  some metrics in other means than XSL transformations. We should try
- *  to implement some metrics with Java. We could start with LCOM4 metric that
- *  implies a graph traversal algorithm.
  */
 public interface Report {
 
diff --git a/src/main/java/org/jpeek/XslCalculus.java b/src/main/java/org/jpeek/XslCalculus.java
new file mode 100644
index 00000000..184d3202
--- /dev/null
+++ b/src/main/java/org/jpeek/XslCalculus.java
@@ -0,0 +1,56 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017-2019 Yegor Bugayenko
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package org.jpeek;
+
+import com.jcabi.xml.Sources;
+import com.jcabi.xml.XML;
+import com.jcabi.xml.XSLDocument;
+import java.io.IOException;
+import java.util.Map;
+import org.cactoos.io.ResourceOf;
+import org.cactoos.text.FormattedText;
+import org.cactoos.text.TextOf;
+
+/**
+ * Metrics xsl calculus. Use an xsl sheet to transform the input skeleton into
+ * the xml containing the calculation.
+ * @since 0.30.9
+ */
+public final class XslCalculus implements Calculus {
+
+    @Override
+    public XML node(final String metric, final Map<String, Object> params,
+        final XML skeleton) throws IOException {
+        return new XSLDocument(
+            new TextOf(
+                new ResourceOf(
+                    new FormattedText("org/jpeek/metrics/%s.xsl", metric)
+                )
+            ).asString(),
+            Sources.DUMMY,
+            params
+        ).transform(skeleton);
+    }
+
+}
diff --git a/src/main/java/org/jpeek/XslReport.java b/src/main/java/org/jpeek/XslReport.java
index 13edf20d..5dea6d2a 100644
--- a/src/main/java/org/jpeek/XslReport.java
+++ b/src/main/java/org/jpeek/XslReport.java
@@ -25,7 +25,6 @@
 
 import com.jcabi.log.Logger;
 import com.jcabi.xml.ClasspathSources;
-import com.jcabi.xml.Sources;
 import com.jcabi.xml.StrictXML;
 import com.jcabi.xml.XML;
 import com.jcabi.xml.XMLDocument;
@@ -39,11 +38,8 @@
 import java.util.HashMap;
 import java.util.Map;
 import org.cactoos.collection.CollectionOf;
-import org.cactoos.io.ResourceOf;
 import org.cactoos.io.TeeInput;
 import org.cactoos.scalar.LengthOf;
-import org.cactoos.text.FormattedText;
-import org.cactoos.text.TextOf;
 import org.xembly.Directives;
 import org.xembly.Xembler;
 
@@ -95,6 +91,11 @@ final class XslReport implements Report {
      */
     private final String metric;
 
+    /**
+     * Calculus.
+     */
+    private final Calculus calculus;
+
     /**
      * Post processing XSLs.
      */
@@ -109,10 +110,11 @@ final class XslReport implements Report {
      * Ctor.
      * @param xml Skeleton
      * @param name Name of the metric
+     * @param calc Calculus
      */
-    XslReport(final XML xml, final String name) {
+    XslReport(final XML xml, final String name, final Calculus calc) {
         this(
-            xml, name, new HashMap<>(0),
+            xml, name, new HashMap<>(0), calc,
             XslReport.DEFAULT_MEAN, XslReport.DEFAULT_SIGMA
         );
     }
@@ -122,10 +124,13 @@ final class XslReport implements Report {
      * @param xml Skeleton
      * @param name Name of metric
      * @param args Params for XSL
+     * @param calc Calculus
+     * @checkstyle ParameterNumberCheck (5 lines)
      */
-    XslReport(final XML xml, final String name, final Map<String, Object> args) {
+    XslReport(final XML xml, final String name, final Map<String, Object> args,
+        final Calculus calc) {
         this(
-            xml, name, args,
+            xml, name, args, calc,
             XslReport.DEFAULT_MEAN, XslReport.DEFAULT_SIGMA
         );
     }
@@ -135,16 +140,24 @@ final class XslReport implements Report {
      * @param xml Skeleton
      * @param name Name of the metric
      * @param args Params for XSL
+     * @param calc Calculus
      * @param mean Mean
      * @param sigma Sigma
+     * @todo #390:30min this constructor now has too many arguments. We should find a way
+     *  to refactor the constructor or the class to have fewer parameters.
+     *  We could start by analyzing the usage of this.params (args in this
+     *  constructor) and get rid of it if it is not used.
+     *  Another idea could be to have a data class contaning reporting params:
+     *  name, args, mean, sigma.
      * @checkstyle ParameterNumberCheck (10 lines)
      */
     XslReport(final XML xml, final String name,
-        final Map<String, Object> args,
+        final Map<String, Object> args, final Calculus calc,
         final double mean, final double sigma) {
         this.skeleton = xml;
         this.metric = name;
         this.params = args;
+        this.calculus = calc;
         this.post = new XSLChain(
             new CollectionOf<>(
                 new XSLDocument(
@@ -227,18 +240,9 @@ private XML xml() throws IOException {
                         XslReport.SCHEMA_FILE
                     )
             ).applyQuietly(
-                new XSLDocument(
-                    new TextOf(
-                        new ResourceOf(
-                            new FormattedText(
-                                "org/jpeek/metrics/%s.xsl",
-                                this.metric
-                            )
-                        )
-                    ).asString(),
-                    Sources.DUMMY,
-                    this.params
-                ).transform(this.skeleton).node()
+                this.calculus.node(
+                    this.metric, this.params, this.skeleton
+                ).node()
             )
         );
     }
diff --git a/src/test/java/org/jpeek/MetricsTest.java b/src/test/java/org/jpeek/MetricsTest.java
index b2dbccfa..9008c801 100644
--- a/src/test/java/org/jpeek/MetricsTest.java
+++ b/src/test/java/org/jpeek/MetricsTest.java
@@ -58,6 +58,7 @@
  * @todo #323:30min This test is fully written against JUnit 4 API.
  *  Migrate this parametrized test to junit 5, so it won't import any classes from junit 4 anymore.
  * @checkstyle JavadocTagsCheck (500 lines)
+ * @checkstyle ClassDataAbstractionCouplingCheck (500 lines)
  */
 @RunWith(Parameterized.class)
 @SuppressWarnings({
@@ -249,7 +250,7 @@ public void testsTarget() throws Exception {
         final Path output = Files.createTempDirectory("");
         new XslReport(
             new Skeleton(new FakeBase(this.target)).xml(),
-            this.metric
+            this.metric, new XslCalculus()
         ).save(output);
         final String xpath;
         if (Double.isNaN(this.value)) {
diff --git a/src/test/java/org/jpeek/XslCalculusTest.java b/src/test/java/org/jpeek/XslCalculusTest.java
new file mode 100644
index 00000000..d240dcc3
--- /dev/null
+++ b/src/test/java/org/jpeek/XslCalculusTest.java
@@ -0,0 +1,75 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017-2019 Yegor Bugayenko
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package org.jpeek;
+
+import com.jcabi.matchers.XhtmlMatchers;
+import com.jcabi.xml.XML;
+import java.io.IOException;
+import java.util.HashMap;
+import org.jpeek.skeleton.Skeleton;
+import org.junit.jupiter.api.Test;
+import org.llorllale.cactoos.matchers.Assertion;
+
+/**
+ * Test case for {@link XslCalculus}.
+ * @since 0.30.9
+ */
+public final class XslCalculusTest {
+
+    @Test
+    public void createsXmlCalculusWithXpaths() throws IOException {
+        final XML result = new XslCalculus().node(
+            "LCOM", new HashMap<>(0), new Skeleton(
+                new FakeBase(
+                    "NoMethods", "Bar", "OverloadMethods",
+                    "OnlyOneMethodWithParams", "WithoutAttributes"
+                )
+            ).xml()
+        );
+        new Assertion<>(
+            "Must create LCOM report",
+            result.toString(),
+            XhtmlMatchers.hasXPaths(
+                "/metric/app/package/class/vars",
+                "/metric/app/package/class/vars/var",
+                "/metric/app/package/class[@value]"
+            )
+        ).affirm();
+    }
+
+    @Test
+    public void createsXmlCalculusWithEmptyProject() throws IOException {
+        final XML result = new XslCalculus().node(
+            "LCOM2", new HashMap<>(0), new Skeleton(new FakeBase()).xml()
+        );
+        new Assertion<>(
+            "Report for empty project created",
+            result.toString(),
+            XhtmlMatchers.hasXPaths(
+                "/metric[title='LCOM2']/app[@id]"
+            )
+        ).affirm();
+    }
+
+}
diff --git a/src/test/java/org/jpeek/XslReportTest.java b/src/test/java/org/jpeek/XslReportTest.java
index 5867ca06..9c8991a1 100644
--- a/src/test/java/org/jpeek/XslReportTest.java
+++ b/src/test/java/org/jpeek/XslReportTest.java
@@ -48,7 +48,9 @@ public final class XslReportTest {
     @Test
     public void createsXmlReport() throws IOException {
         final Path output = Files.createTempDirectory("");
-        new XslReport(new Skeleton(new FakeBase()).xml(), "LCOM").save(output);
+        new XslReport(
+            new Skeleton(new FakeBase()).xml(), "LCOM", new XslCalculus()
+        ).save(output);
         new Assertion<>(
             "Must LCOM.xml file exists",
             Files.exists(output.resolve("LCOM.xml")),
@@ -71,7 +73,7 @@ public void createsXmlReportWithXpaths() throws IOException {
                     "OnlyOneMethodWithParams", "WithoutAttributes"
                 )
             ).xml(),
-            "LCOM"
+            "LCOM", new XslCalculus()
         ).save(output);
         new Assertion<>(
             "Must create LCOM report",
@@ -79,7 +81,6 @@ public void createsXmlReportWithXpaths() throws IOException {
                 new TextOf(output.resolve("LCOM.xml")).asString()
             ),
             XhtmlMatchers.hasXPaths(
-                "/metric/app/package/class/vars",
                 "/metric/statistics/mean",
                 "/metric/bars/bar[@x='0' and .='0' and @color='yellow']"
             )
@@ -89,7 +90,9 @@ public void createsXmlReportWithXpaths() throws IOException {
     @Test
     public void createsXmlReportWithEmptyProject() throws IOException {
         final Path output = Files.createTempDirectory("");
-        new XslReport(new Skeleton(new FakeBase()).xml(), "LCOM").save(output);
+        new XslReport(
+            new Skeleton(new FakeBase()).xml(), "LCOM", new XslCalculus()
+        ).save(output);
         new Assertion<>(
             "Report for empty project created",
             XhtmlMatchers.xhtml(
@@ -119,7 +122,7 @@ public void createsFullXmlReport() throws IOException {
                         .add("class").attr("id", "E").attr("value", "NaN").up()
                 ).xmlQuietly()
             ),
-            "LCOM"
+            "LCOM", new XslCalculus()
         ).save(output);
         new Assertion<>(
             "Must create full report",
@@ -141,7 +144,9 @@ public void createsFullXmlReport() throws IOException {
     @Test
     public void setsCorrectSchemaLocation() throws IOException {
         final Path output = Files.createTempDirectory("");
-        new XslReport(new Skeleton(new FakeBase()).xml(), "LCOM").save(output);
+        new XslReport(
+            new Skeleton(new FakeBase()).xml(), "LCOM", new XslCalculus()
+        ).save(output);
         new Assertion<>(
             "Must have correct schema location",
             XhtmlMatchers.xhtml(