Merge pull request eugenp#6143 from dionisPrifti/BAEL-2441-Java-Enums-for_State-Machines

BAEL-2441: Providing example for State Machines with Enums

Author: eric-martin

algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/enumstatemachine/LeaveRequestState.java

@@ -0,0 +1,46 @@
+package com.baeldung.algorithms.enumstatemachine;
+
+public enum LeaveRequestState {
+
+    Submitted {
+        @Override
+        public LeaveRequestState nextState() {
+            System.out.println("Starting the Leave Request and sending to Team Leader for approval.");
+            return Escalated;
+        }
+
+        @Override
+        public String responsiblePerson() {
+            return "Employee";
+        }
+    },
+    Escalated {
+        @Override
+        public LeaveRequestState nextState() {
+            System.out.println("Reviewing the Leave Request and escalating to Department Manager.");
+            return Approved;
+        }
+
+        @Override
+        public String responsiblePerson() {
+            return "Team Leader";
+        }
+    },
+    Approved {
+        @Override
+        public LeaveRequestState nextState() {
+            System.out.println("Approving the Leave Request.");
+            return this;
+        }
+
+        @Override
+        public String responsiblePerson() {
+            return "Department Manager";
+        }
+    };
+
+    public abstract String responsiblePerson();
+
+    public abstract LeaveRequestState nextState();
+
+}

algorithms-miscellaneous-1/src/test/java/com/baeldung/algorithms/enumstatemachine/LeaveRequestStateUnitTest.java

@@ -0,0 +1,37 @@
+package com.baeldung.algorithms.enumstatemachine;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class LeaveRequestStateUnitTest {
+
+    @Test
+    public void givenLeaveRequest_whenStateEscalated_thenResponsibleIsTeamLeader() {
+        LeaveRequestState state = LeaveRequestState.Escalated;
+
+        assertEquals(state.responsiblePerson(), "Team Leader");
+    }
+
+
+    @Test
+    public void givenLeaveRequest_whenStateApproved_thenResponsibleIsDepartmentManager() {
+        LeaveRequestState state = LeaveRequestState.Approved;
+
+        assertEquals(state.responsiblePerson(), "Department Manager");
+    }
+
+    @Test
+    public void givenLeaveRequest_whenNextStateIsCalled_thenStateIsChanged() {
+        LeaveRequestState state = LeaveRequestState.Submitted;
+
+        state = state.nextState();
+        assertEquals(state, LeaveRequestState.Escalated);
+
+        state = state.nextState();
+        assertEquals(state, LeaveRequestState.Approved);
+
+        state = state.nextState();
+        assertEquals(state, LeaveRequestState.Approved);
+    }
+}