style: enable AvoidNestedBlocks in checkstyle (#5228)

* enable style AvoidNestedBlocks

* refactor after enable style AvoidNestedBlocks

* fix clang

* fix checkstyle

* fix pmd

---------

Co-authored-by: Samuel Facchinello <samuel.facchinello@piksel.com>
Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com>

src/test/java/com/thealgorithms/maths/MatrixUtilTest.java

@@ -0,0 +1,79 @@
+package com.thealgorithms.maths;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.math.BigDecimal;
+import java.util.Objects;
+import org.junit.jupiter.api.Test;
+
+class MatrixUtilTest {
+
+    @Test
+    void add() {
+        final BigDecimal[][] matrix1 = {
+            {new BigDecimal(3), new BigDecimal(2)},
+            {BigDecimal.ZERO, BigDecimal.ONE},
+        };
+
+        final BigDecimal[][] matrix2 = {
+            {BigDecimal.ONE, new BigDecimal(3)},
+            {new BigDecimal(2), BigDecimal.ZERO},
+        };
+
+        final BigDecimal[][] actual = MatrixUtil.add(matrix1, matrix2).orElseThrow(() -> new AssertionError("Could not compute matrix!"));
+
+        final BigDecimal[][] expected = {
+            {new BigDecimal(4), new BigDecimal(5)},
+            {new BigDecimal(2), BigDecimal.ONE},
+        };
+
+        assertTrue(Objects.deepEquals(actual, expected));
+    }
+    @Test
+    void subtract() {
+        final BigDecimal[][] matrix1 = {
+            {BigDecimal.ONE, new BigDecimal(4)},
+            {new BigDecimal(5), new BigDecimal(6)},
+        };
+
+        final BigDecimal[][] matrix2 = {
+            {new BigDecimal(2), BigDecimal.ZERO},
+            {new BigDecimal(-2), new BigDecimal(-3)},
+        };
+
+        final BigDecimal[][] actual = MatrixUtil.subtract(matrix1, matrix2).orElseThrow(() -> new AssertionError("Could not compute matrix!"));
+
+        final BigDecimal[][] expected = {
+            {new BigDecimal(-1), new BigDecimal(4)},
+            {new BigDecimal(7), new BigDecimal(9)},
+        };
+
+        assertTrue(Objects.deepEquals(actual, expected));
+    }
+
+    @Test
+    void multiply() {
+
+        final BigDecimal[][] matrix1 = {
+            {BigDecimal.ONE, new BigDecimal(2), new BigDecimal(3)},
+            {new BigDecimal(4), new BigDecimal(5), new BigDecimal(6)},
+            {new BigDecimal(7), new BigDecimal(8), new BigDecimal(9)},
+        };
+
+        final BigDecimal[][] matrix2 = {
+            {BigDecimal.ONE, new BigDecimal(2)},
+            {new BigDecimal(3), new BigDecimal(4)},
+            {new BigDecimal(5), new BigDecimal(6)},
+        };
+
+        final BigDecimal[][] actual = MatrixUtil.multiply(matrix1, matrix2).orElseThrow(() -> new AssertionError("Could not compute matrix!"));
+
+        final BigDecimal[][] expected = {
+            {new BigDecimal(22), new BigDecimal(28)},
+            {new BigDecimal(49), new BigDecimal(64)},
+            {new BigDecimal(76), new BigDecimal(100)},
+        };
+
+        assertTrue(Objects.deepEquals(actual, expected));
+    }
+}