example for multi-release jar

core-java-9/src/main/java/com/baeldung/multireleaseapp/App.java

@@ -0,0 +1,11 @@
+package com.baeldung.multireleaseapp;
+
+public class App {
+
+    public static void main(String[] args) throws Exception {
+        String dateToCheck = args[0];
+        boolean isLeapYear = DateHelper.checkIfLeapYear(dateToCheck);
+        System.out.println("Date given " + dateToCheck + " is leap year: " + isLeapYear);
+    }
+
+}

core-java-9/src/main/java/com/baeldung/multireleaseapp/DateHelper.java

@@ -0,0 +1,24 @@
+package com.baeldung.multireleaseapp;
+
+import java.text.SimpleDateFormat;
+import java.util.Calendar;
+
+public class DateHelper {
+
+    public static boolean checkIfLeapYear(String dateStr) throws Exception {
+        System.out.println("Checking for leap year using Java 1 calendar API ");
+        boolean isLeapYear = false;
+        Calendar cal = Calendar.getInstance();
+        cal.setTime(new SimpleDateFormat("yyyy-MM-dd").parse(dateStr));
+        int year = cal.get(Calendar.YEAR);
+        if (year % 4 == 0) {
+            if (year % 100 == 0) {
+                isLeapYear = (year % 400 == 0) ? true : false;
+            } else {
+                isLeapYear = true;
+            }
+        }
+        return isLeapYear;
+    }
+
+}

core-java-9/src/main/java9/com/baeldung/multireleaseapp/DateHelper.java

@@ -0,0 +1,13 @@
+package com.baeldung.multireleaseapp;
+
+import java.time.LocalDate;
+
+public class DateHelper {
+
+    public static boolean checkIfLeapYear(String dateStr) throws Exception {
+        System.out.println("Checking for leap year using Java 9 Date Api");
+        return LocalDate.parse(dateStr)
+            .isLeapYear();
+    }
+
+}