Add data operations tests ...

basics/src/test/java/pl/mperor/lab/java/data/operation/BasicArithmeticTest.java

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+package pl.mperor.lab.java.data.operation;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+public class BasicArithmeticTest {
+
+    @Test
+    public void testDividingDoubleVsInt() {
+        Assertions.assertTrue(3 == 16 / 5);
+        Assertions.assertTrue(3.2 == (double) 16 / 5);
+    }
+
+    @Test
+    public void testDividingDoubleByZero() {
+        Assertions.assertEquals(Double.POSITIVE_INFINITY, 3.0 / 0);
+        Assertions.assertEquals(Double.NEGATIVE_INFINITY, -3.0 / 0);
+        Assertions.assertEquals(0, 0 / 4.0);
+        Assertions.assertTrue(Double.isNaN(0 / 0.0));
+    }
+
+    @Test
+    public void testDividingIntegerByZero() {
+        assertThrows(ArithmeticException.class, () -> {
+            int _ = 3 / 0;
+        });
+        assertEquals(0, 0 / 4);
+        assertThrows(ArithmeticException.class, () -> {
+            int _ = 0 / 0;
+        });
+    }
+
+    @Test
+    public void testBigDecimalDividing() {
+        BigDecimal two = BigDecimal.TWO;
+        BigDecimal three = BigDecimal.valueOf(3);
+        Assertions.assertThrows(ArithmeticException.class, () -> two.setScale(2).divide(three));
+        Assertions.assertEquals(new BigDecimal("0.67"), two.setScale(2).divide(three, RoundingMode.HALF_UP));
+    }
+
+    @Test
+    public void testFloatingPointAccuracy() {
+        Assertions.assertTrue(0.1 == 1.0 / 10.0);
+        Assertions.assertEquals(0.1, 0.3 - 0.2, 1e-9);
+    }
+
+    @Test
+    public void testMathApi() {
+        Assertions.assertEquals(5, Math.abs(-5));
+        Assertions.assertEquals(1, Math.min(1, 2));
+        Assertions.assertEquals(2, Math.max(1, 2));
+        Assertions.assertEquals(27, Math.pow(3, 3));
+        Assertions.assertEquals(4, Math.sqrt(16));
+        Assertions.assertEquals(Double.NaN, Math.sqrt(-1));
+        Assertions.assertEquals(3.14, Math.round(Math.PI * 100) / 100.0);
+    }
+}

basics/src/test/java/pl/mperor/lab/java/data/operation/ExpressionTypeTest.java

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+package pl.mperor.lab.java.data.operation;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class ExpressionTypeTest {
+
+    @Test
+    public void testExpressionVsStatement() {
+        byte b = 1;
+        Assertions.assertEquals(2, b + b, "statement");
+        int expression = b + b;
+        Assertions.assertEquals(2, expression, "expression");
+    }
+
+    @Test
+    public void testTypeOfArithmeticExpression() {
+        byte b = 1;
+        Assertions.assertInstanceOf(Integer.class, b + b);
+        short s = 2;
+        Assertions.assertInstanceOf(Integer.class, s + s);
+        Assertions.assertInstanceOf(Long.class, 1 + 1L);
+
+        Assertions.assertInstanceOf(Float.class, 1.0f + 1.0f);
+        Assertions.assertInstanceOf(Double.class, 1 + 1.0);
+        Assertions.assertInstanceOf(Double.class, 1.0f + 1.0);
+        Assertions.assertInstanceOf(String.class, "" + 1.0);
+    }
+
+}

basics/src/test/java/pl/mperor/lab/java/data/operation/OperatorsTest.java

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+package pl.mperor.lab.java.data.operation;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class OperatorsTest {
+
+    @Test
+    public void testUnaryArithmeticOperators() {
+        Assertions.assertEquals(1, +1, "plus");
+        Assertions.assertEquals(-1, -1, "minus");
+        int i = 10;
+        Assertions.assertEquals(10, i++, "post-increment");
+        Assertions.assertEquals(10, --i, "pre-decrement");
+    }
+
+    @Test
+    public void testBinaryArithmeticOperators() {
+        Assertions.assertEquals(3, 1 + 2, "addition");
+        Assertions.assertEquals(1, 2 - 1, "subtraction");
+        Assertions.assertEquals(4, 2 * 2, "multiplication");
+        Assertions.assertEquals(2, 4 / 2, "division");
+        Assertions.assertEquals(2, 5 % 3, "modulo");
+        Assertions.assertEquals("ab", "a" + "b", "string concatenation");
+    }
+
+    @Test
+    public void testAssignmentOperators() {
+        int i = 1;
+        i *= 2; // same as i = i * 2;
+        String s = "a";
+        s += "b";
+        Assertions.assertEquals(2, i);
+        Assertions.assertEquals("ab", s);
+    }
+
+    @Test
+    public void testComparisonOperators() {
+        Assertions.assertTrue(1 == 1, "equals to");
+        Assertions.assertTrue(1 != 2, "not equals to");
+        Assertions.assertTrue(2 > 1, "greater than");
+        Assertions.assertTrue(1 < 2, "less than");
+        Assertions.assertFalse(2 >= 4, "greater than or equals to");
+        Assertions.assertFalse(4 <= 2, "less than or equals to");
+    }
+
+    @Test
+    public void testLogicalOperators() {
+        Assertions.assertTrue(true & true, "and");
+        Assertions.assertFalse(false && true, "short and");
+        Assertions.assertTrue(true | true, "or");
+        Assertions.assertTrue(false || true, "short or");
+        Assertions.assertFalse(!true, "not");
+        Assertions.assertFalse(true ^ true, "xor");
+    }
+
+    @Test
+    public void testBitwiseOperators() {
+        Assertions.assertEquals(0b0001, 0b1001 & 0b0011, "and");
+        Assertions.assertEquals(0b1011, 0b1001 | 0b0011, "or");
+        Assertions.assertEquals(0b1010, 0b1001 ^ 0b0011, "xor");
+        Assertions.assertEquals(0b11111111_11111111_11111111_11110110, ~0b1001, "flip");
+        Assertions.assertEquals(0b0110, 0b0011 << 1, "left shift");
+        Assertions.assertEquals(0b0001, 0b0011 >> 1, "right shift");
+        Assertions.assertEquals(
+                0b01000000_00000000_00000000_00000000,
+                0b10000000_00000000_00000000_00000001 >>> 1,
+                "unsigned right shift"
+        );
+    }
+
+    @Test
+    public void testTernaryOperator() {
+        Assertions.assertTrue(isEmpty(null));
+        Assertions.assertTrue(isEmpty(""));
+        Assertions.assertFalse(isEmpty("not empty"));
+    }
+
+    private static boolean isEmpty(String string) {
+        return string == null ? true : string.isEmpty();
+    }
+
+}

basics/src/test/java/pl/mperor/lab/java/data/operation/PrimitiveAndReferenceTypesComparisonTest.java

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+package pl.mperor.lab.java.data.operation;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+
+public class PrimitiveAndReferenceTypesComparisonTest {
+
+    @Test
+    public void testComparePrimitiveTypes() {
+        Assertions.assertTrue(1 == 1);
+        Assertions.assertFalse(1 == 2);
+        Assertions.assertTrue(65 == 'A');
+    }
+
+    @SuppressWarnings("removal")
+    @Test
+    public void testCompareReferenceTypes() {
+        Assertions.assertTrue(Integer.valueOf(127) == Integer.valueOf(127), "Integer pool (-128, 127)");
+        Assertions.assertFalse(Integer.valueOf(128) == Integer.valueOf(128));
+
+        Assertions.assertTrue(new Integer(1).equals(new Integer(1)), "equals to");
+        Assertions.assertFalse(new Integer(1) == new Integer(1), "==");
+    }
+
+    @Test
+    public void testCompareArrays() {
+        int[] a1 = {1, 2, 3}, a2 = {1, 2, 3};
+        Assertions.assertFalse(a1 == a2);
+        Assertions.assertFalse((a1.equals(a2)));
+        Assertions.assertTrue(Arrays.equals(a1, a2));
+    }
+}