BAEL-5291 Convert String to Float and back in Java (#11619)

* add hexagonal architecture example project

* rename class

* add unit test and integration test

* add new line

* reorder pom

* remove maven wrapper

* BAEL-5291 unit tests to showcase conversion from String to Float and back

* BAEL-5291 add some more unit tests

* BAEL-5291 remove evaluation module

* BAEL-5291 rename method names

core-java-modules/core-java-string-conversions-2/src/test/java/com/baeldung/stringtofloat/StringToFloatConversionUnitTest.java

@@ -0,0 +1,187 @@
+package com.baeldung.stringtofloat;
+
+import org.junit.jupiter.api.Test;
+
+import java.text.DecimalFormat;
+import java.text.DecimalFormatSymbols;
+import java.text.ParseException;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+public class StringToFloatConversionUnitTest {
+
+    @Test
+    public void givenFloat_whenStringConcatenation_thenReturnString() {
+        Float givenFloat = 1.25f;
+
+        String result = givenFloat + "";
+
+        assertEquals("1.25", result);
+    }
+
+    @Test
+    public void givenFloatPrimitive_whenStringConcatenation_thenReturnString() {
+        float givenFloat = 1.25f;
+
+        String result = givenFloat + "";
+
+        assertEquals("1.25", result);
+    }
+
+    @Test
+    public void givenNullFloat_whenStringConcatenation_thenReturnNullString() {
+        Float givenFloat = null;
+
+        String result = givenFloat + "";
+
+        assertEquals("null", result);
+    }
+
+    @Test
+    public void givenFloat_whenToString_thenReturnString() {
+        Float givenFloat = 1.25f;
+
+        String result = Float.toString(givenFloat);
+
+        assertEquals("1.25", result);
+    }
+
+    @Test
+    public void givenNullFloat_whenToString_thenThrowNullPointerException() {
+        Float givenFloat = null;
+
+        assertThrows(NullPointerException.class, () -> Float.toString(givenFloat));
+    }
+
+    @Test
+    public void givenFloat_whenValueOf_thenReturnString() {
+        Float givenFloat = 1.25f;
+
+        String result = String.valueOf(givenFloat);
+
+        assertEquals("1.25", result);
+    }
+
+    @Test
+    public void givenNullFloat_whenValueOf_thenReturnNullString() {
+        Float givenFloat = null;
+
+        String result = String.valueOf(givenFloat);
+
+        assertEquals("null", result);
+    }
+
+    @Test
+    public void givenFloat_whenDecimalFormat_thenReturnString() {
+        Float givenFloat = 1.25f;
+
+        String result = new DecimalFormat("#.0000").format(givenFloat);
+
+        assertEquals("1.2500", result);
+    }
+
+    @Test
+    public void givenFloat_whenDecimalFormat_thenReturnWholeNumberString() {
+        Float givenFloat = 1.0025f;
+
+        String result = new DecimalFormat("#.##").format(givenFloat);
+
+        assertEquals("1", result);
+    }
+
+    @Test
+    public void givenNullFloat_whenDecimalFormat_thenThrowIllegalArgumentException() {
+        Float givenFloat = null;
+
+        assertThrows(IllegalArgumentException.class, () -> new DecimalFormat("#.000").format(givenFloat));
+    }
+
+    @Test
+    public void givenFloat_whenStringFormat_thenReturnString() {
+        Float givenFloat = 1.25f;
+
+        String result = String.format("%f", givenFloat);
+
+        assertEquals("1.250000", result);
+    }
+
+    @Test
+    public void givenFloat_whenStringFormatWithDecimalLimit_thenReturnRoundedString() {
+        Float givenFloat = 1.256f;
+
+        String result = String.format("%.2f", givenFloat);
+
+        assertEquals("1.26", result);
+    }
+
+    @Test
+    public void givenNullFloat_whenStringFormatWithDecimalLimit_thenReturnNullString() {
+        Float givenFloat = null;
+
+        String result = String.format("%f", givenFloat);
+
+        assertEquals("null", result);
+    }
+
+    @Test
+    public void givenString_whenParseFloat_thenReturnFloat() {
+        String givenString = "1.25";
+
+        float result = Float.parseFloat(givenString);
+
+        assertEquals(1.25f, result);
+    }
+
+    @Test
+    public void givenNullString_whenParseFloat_thenThrowNullPointerException() {
+        String givenString = null;
+
+        assertThrows(NullPointerException.class, () -> Float.parseFloat(givenString));
+    }
+
+    @Test
+    public void givenNonParsableString_whenParseFloat_thenThrowNumberFormatException() {
+        String givenString = "1.23x";
+
+        assertThrows(NumberFormatException.class, () -> Float.parseFloat(givenString));
+    }
+
+    @Test
+    public void givenString_whenValueOf_thenReturnFloat() {
+        String givenString = "1.25";
+
+        Float result = Float.valueOf(givenString);
+
+        assertEquals(1.25f, result);
+    }
+
+    @Test
+    public void givenNonParsableString_whenValueOf_thenThrowNumberFormatException() {
+        String givenString = "1.25x";
+
+        assertThrows(NumberFormatException.class, () -> Float.valueOf(givenString));
+    }
+
+    @Test
+    public void givenString_whenConstructor_thenReturnFloat() {
+        String givenString = "1.25";
+
+        Float result = new Float(givenString);
+
+        assertEquals(1.25f, result);
+    }
+
+    @Test
+    public void givenString_whenDecimalFormat_thenReturnFloat() throws ParseException {
+        String givenString = "1,250";
+        DecimalFormatSymbols symbols = new DecimalFormatSymbols();
+        symbols.setDecimalSeparator(',');
+        DecimalFormat decimalFormat = new DecimalFormat("#.000");
+        decimalFormat.setDecimalFormatSymbols(symbols);
+
+        Float result = decimalFormat.parse(givenString).floatValue();
+
+        assertEquals(1.25f, result);
+    }
+}