[BAEL-2996] Added la4j library example

libraries-2/pom.xml

@@ -60,6 +60,11 @@
 			<artifactId>colt</artifactId>
 			<version>${colt.version}</version>
 		</dependency>
+		<dependency>
+			<groupId>org.la4j</groupId>
+			<artifactId>la4j</artifactId>
+			<version>${la4j.version}</version>
+		</dependency>
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter</artifactId>
@@ -121,5 +126,6 @@
 		<spring-boot-starter.version>2.1.4.RELEASE</spring-boot-starter.version>
 		<ejml.version>0.37.1</ejml.version>
 		<colt.version>1.2.0</colt.version>
+		<la4j.version>0.6.0</la4j.version>
 	</properties>
 </project>

libraries-2/src/test/java/com/baeldung/colt/DoubleMatrix2DUnitTest.java

@@ -7,7 +7,7 @@ import org.junit.jupiter.api.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
-class DoubleMatrix2DUniTest {
+class DoubleMatrix2DUnitTest {
 
     @Test
     void givenTwoMatrices_whenMultiply_thenMultiplicatedMatrix() {

libraries-2/src/test/java/com/baeldung/la4j/Basic2DMatrixUnitTest.java

@@ -0,0 +1,39 @@
+package com.baeldung.la4j;
+
+import org.junit.jupiter.api.Test;
+import org.la4j.Matrix;
+import org.la4j.matrix.dense.Basic2DMatrix;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class Basic2DMatrixUnitTest {
+
+    @Test
+    void givenTwoMatrices_whenMultiply_thenMultiplicatedMatrix() {
+        Matrix firstMatrix = new Basic2DMatrix(
+          new double[][]{
+            new double[]{1d, 5d},
+            new double[]{2d, 3d},
+            new double[]{1d, 7d}
+          });
+
+        Matrix secondMatrix = new Basic2DMatrix(
+          new double[][]{
+            new double[]{1d, 2d, 3d, 7d},
+            new double[]{5d, 2d, 8d, 1d}
+          }
+        );
+
+        Matrix expected = new Basic2DMatrix(
+          new double[][]{
+            new double[]{26d, 12d, 43d, 12d},
+            new double[]{17d, 10d, 30d, 17d},
+            new double[]{36d, 16d, 59d, 14d}
+          }
+        );
+
+        Matrix actual = firstMatrix.multiply(secondMatrix);
+
+        assertThat(actual).isEqualTo(expected);
+    }
+}