BAEL-5178:An introduction to InstantSource (#11646)

* BAEL-5178:An introduction to InstantSource

* BAEL-5178:PR fixes

Co-authored-by: Pablo Ubal <pablo.ubal@flexit.es>

core-java-modules/core-java-17/src/main/java/com/baeldung/instantsource/InstantExample.java

@@ -0,0 +1,21 @@
+package com.baeldung.instantsource;
+
+import java.time.Instant;
+import java.time.InstantSource;
+
+public class InstantExample {
+    InstantWrapper instantWrapper;
+    InstantSource instantSource;
+
+    public InstantExample(InstantWrapper instantWrapper, InstantSource instantSource) {
+        this.instantWrapper = instantWrapper;
+        this.instantSource = instantSource;
+    }
+
+    public Instant getCurrentInstantFromWrapper() {
+        return instantWrapper.instant();
+    }
+    public Instant getCurrentInstantFromInstantSource() {
+        return instantSource.instant();
+    }
+}

core-java-modules/core-java-17/src/main/java/com/baeldung/instantsource/InstantWrapper.java

@@ -0,0 +1,39 @@
+package com.baeldung.instantsource;
+
+import java.time.Clock;
+import java.time.Instant;
+import java.time.LocalDateTime;
+import java.time.ZoneOffset;
+import java.time.ZonedDateTime;
+
+public class InstantWrapper {
+    Clock clock;
+
+    private InstantWrapper() {
+        this.clock = Clock.systemDefaultZone();
+    }
+
+    private InstantWrapper(ZonedDateTime zonedDateTime) {
+        this.clock = Clock.fixed(zonedDateTime.toInstant(), zonedDateTime.getZone());
+    }
+
+    private InstantWrapper(LocalDateTime localDateTime) {
+        this.clock = Clock.fixed(localDateTime.toInstant(ZoneOffset.UTC), ZoneOffset.UTC);
+    }
+
+    public static InstantWrapper of() {
+        return new InstantWrapper();
+    }
+
+    public static InstantWrapper of(ZonedDateTime zonedDateTime) {
+        return new InstantWrapper(zonedDateTime);
+    }
+
+    public static InstantWrapper of(LocalDateTime localDateTime) {
+        return new InstantWrapper(localDateTime);
+    }
+
+    public Instant instant() {
+        return clock.instant();
+    }
+}