Javadoublevsbigdecimal (#14862)

* Create BigDecimalConversionUnitTest.java

* Add files via upload

* Update BigDecimalConversionUnitTest.java

* Update BigDecimalConversionUnitTest.java

* Update BigDecimalConversionUnitTest.java

core-java-modules/core-java-numbers-6/src/test/java/com/baeldung/javadoublevsbigdecimal/BigDecimalConversionUnitTest.java

@@ -0,0 +1,28 @@
+package com.baeldung.javadoublevsbigdecimal;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+
+import org.junit.jupiter.api.Test;
+
+public class BigDecimalConversionUnitTest {
+
+    @Test
+    void whenConvertingDoubleToBigDecimal_thenConversionIsCorrect() {
+        double doubleValue = 123.456;
+        BigDecimal bigDecimalValue = BigDecimal.valueOf(doubleValue);
+        BigDecimal expected = new BigDecimal("123.456").setScale(3, RoundingMode.HALF_UP);
+        assertEquals(expected, bigDecimalValue.setScale(3, RoundingMode.HALF_UP));
+    }
+
+    @Test
+    void givenDecimalPlacesGreaterThan15_whenConvertingBigDecimalToDouble_thenPrecisionIsLost() {
+        BigDecimal bigDecimalValue = new BigDecimal("789.1234567890123456");
+        double doubleValue = bigDecimalValue.doubleValue();
+        BigDecimal convertedBackToBigDecimal = BigDecimal.valueOf(doubleValue);
+        assertNotEquals(bigDecimalValue, convertedBackToBigDecimal);
+    }
+}

core-java-modules/core-java-numbers-6/src/test/java/com/baeldung/javadoublevsbigdecimal/BigDecimalUnitTest.java

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+package com.baeldung.javadoublevsbigdecimal;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+
+import org.junit.jupiter.api.Test;
+
+public class BigDecimalUnitTest {
+
+    private BigDecimal bigDecimal1 = new BigDecimal("124567890.0987654321");
+    private BigDecimal bigDecimal2 = new BigDecimal("987654321.123456789");
+
+    @Test
+    public void givenTwoBigDecimals_whenAdd_thenCorrect() {
+        BigDecimal expected = new BigDecimal("1112222211.2222222211");
+        BigDecimal actual = bigDecimal1.add(bigDecimal2);
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void givenTwoBigDecimals_whenMultiply_thenCorrect() {
+        BigDecimal expected = new BigDecimal("123030014929277547.5030955772112635269");
+        BigDecimal actual = bigDecimal1.multiply(bigDecimal2);
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void givenTwoBigDecimals_whenSubtract_thenCorrect() {
+        BigDecimal expected = new BigDecimal("-863086431.0246913569");
+        BigDecimal actual = bigDecimal1.subtract(bigDecimal2);
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void givenTwoBigDecimals_whenDivide_thenCorrect() {
+        BigDecimal expected = new BigDecimal("0.13");
+        BigDecimal actual = bigDecimal1.divide(bigDecimal2, 2, RoundingMode.HALF_UP);
+        assertEquals(expected, actual);
+    }
+}

core-java-modules/core-java-numbers-6/src/test/java/com/baeldung/javadoublevsbigdecimal/JavaDoubleUnitTest.java

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+package com.baeldung.javadoublevsbigdecimal;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+public class JavaDoubleUnitTest {
+
+    @Test
+    public void givenDoubleLiteral_whenAssigningToDoubleVariable_thenValueIsNotExactlyEqual() {
+        double doubleValue = 0.1;
+        double epsilon = 0.0000000000000001;
+        assertEquals(0.1, doubleValue, epsilon);
+    }
+}