BAEL-2132 - Date to String conversion (#5116)

* BAEL-2132 - Date to String conversion

* BAEL-2132 - TimeZone set to CET

java-strings/src/test/java/com/baeldung/string/formatter/DateToStringFormatterUnitTest.java

@@ -0,0 +1,67 @@
+package com.baeldung.string.formatter;
+
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.text.DateFormat;
+import java.text.SimpleDateFormat;
+import java.time.Instant;
+import java.time.LocalDateTime;
+import java.time.ZoneId;
+import java.time.format.DateTimeFormatter;
+import java.util.Calendar;
+import java.util.Date;
+import java.util.TimeZone;
+
+import static org.junit.Assert.assertEquals;
+
+public class DateToStringFormatterUnitTest {
+
+    private static final String DATE_FORMAT = "MMM d, yyyy HH:mm a";
+    private static final String EXPECTED_STRING_DATE = "Aug 1, 2018 12:00 PM";
+    private static Date date;
+
+    @BeforeClass
+    public static void setUp() {
+        TimeZone.setDefault(TimeZone.getTimeZone("CET"));
+        Calendar calendar = Calendar.getInstance();
+        calendar.set(2018, Calendar.AUGUST, 1, 12, 0);
+        date = calendar.getTime();
+    }
+
+    @Test
+    public void whenDateConvertedUsingSimpleDateFormatToString_thenCorrect() {
+        DateFormat formatter = new SimpleDateFormat(DATE_FORMAT);
+        String formattedDate = formatter.format(date);
+
+        assertEquals(EXPECTED_STRING_DATE, formattedDate);
+    }
+
+    @Test
+    public void whenDateConvertedUsingDateFormatToString_thenCorrect() {
+        String formattedDate = DateFormat
+          .getDateTimeInstance(DateFormat.MEDIUM, DateFormat.SHORT)
+          .format(date);
+
+        assertEquals(EXPECTED_STRING_DATE, formattedDate);
+    }
+
+    @Test
+    public void whenDateConvertedUsingFormatterToString_thenCorrect() {
+        String formattedDate = String.format("%1$tb %1$te, %1$tY %1$tI:%1$tM %1$Tp", date);
+
+        assertEquals(EXPECTED_STRING_DATE, formattedDate);
+    }
+
+    @Test
+    public void whenDateConvertedUsingDateTimeApiToString_thenCorrect() {
+        DateTimeFormatter fmt = DateTimeFormatter.ofPattern(DATE_FORMAT);
+        Instant instant = date.toInstant();
+        LocalDateTime ldt = instant
+          .atZone(ZoneId.of("CET"))
+          .toLocalDateTime();
+        String formattedDate = ldt.format(fmt);
+
+        assertEquals(EXPECTED_STRING_DATE, formattedDate);
+    }
+}