added possibility to start state machine from custom state

src/main/java/me/bvn13/fsm/Fsm.java

@@ -13,6 +13,8 @@ import java.util.List;
 import java.util.Map;
 import java.util.function.Supplier;
 
+import static java.lang.String.format;
+
 /**
  * <p>
  * <b>Final State Machine</b>
@@ -239,6 +241,20 @@ public class Fsm<T extends Fsm, E> {
         addTransition(fromState, toState.getName(), condition);
     }
 
+    /**
+     * Provides a possibility to initialize FSM in custom State
+     * @param name State name (must be added before)
+     */
+    protected void setCurrentState(String name) {
+        try {
+            this.currentState = this.states.get(name);
+        } catch (NullPointerException e) {
+            throw new NotInitializedException(format("Unable to find state '%s'", name), e);
+        }
+        this.done = currentState.isFinish();
+        this.currentState.beforeEvent();
+    }
+
     private void switchToNextState(E event) {
         if (!transitions.containsKey(currentState.getName())) {
             throw new TransitionMissedException(currentState.getName());

src/main/java/me/bvn13/fsm/FsmBuilder.java

@@ -31,6 +31,11 @@ public class FsmBuilder<T extends Fsm, E> {
         return fsm;
     }
 
+    public T startingAt(String name) {
+        fsm.setCurrentState(name);
+        return fsm;
+    }
+
     T getFsm() {
         return fsm;
     }

src/main/java/me/bvn13/fsm/exceptions/AmbiguousTransitionException.java

@@ -2,6 +2,8 @@ package me.bvn13.fsm.exceptions;
 
 import java.util.List;
 
+import static java.lang.String.format;
+
 /**
  * is thrown if there are more than 1 appropriate transition from current state
  */
@@ -10,11 +12,14 @@ public class AmbiguousTransitionException extends FsmException {
         super(message);
     }
     public AmbiguousTransitionException(String from, List<String> next) {
-        super("");
-        String msg = "";
-        for (String to : next) {
-            msg += (msg.length() > 0 ? ", " : "") + to;
+        super(format("Ambiguous transition from state %s. Candidates are: %s", from, join(next)));
+    }
+
+    private static String join(List<String> list) {
+        StringBuilder msg = new StringBuilder();
+        for (String to : list) {
+            msg.append(msg.length() > 0 ? ", " : "").append(to);
         }
-        this.message = String.format("Ambiguous transition from state %s. Candidates are: %s", from, msg);
+        return msg.toString();
     }
 }

src/main/java/me/bvn13/fsm/exceptions/FsmException.java

@@ -1,23 +1,14 @@
 package me.bvn13.fsm.exceptions;
 
-import java.io.PrintWriter;
-import java.io.StringWriter;
-
 /**
  * Parent FSM exception class
  */
 public class FsmException extends RuntimeException {
-    protected String message;
     public FsmException(String message) {
-        this.message = message;
+        super(message);
     }
-    protected String getStackTraceString() {
-        StringWriter sw = new StringWriter();
-        PrintWriter pw = new PrintWriter(sw);
-        this.printStackTrace(pw);
-        return sw.toString();
-    }
-    public void printStackTrace() {
-        System.out.println(String.format("FSMException: %s / %s", message, getStackTraceString()));
+
+    public FsmException(String message, Throwable cause) {
+        super(message, cause);
     }
 }

src/main/java/me/bvn13/fsm/exceptions/NotInitializedException.java

@@ -7,7 +7,12 @@ public class NotInitializedException extends FsmException {
     public NotInitializedException(String message) {
         super(message);
     }
+
+    public NotInitializedException(String message, Exception e) {
+        super(message, e);
+    }
+
     public NotInitializedException() {
-        super("FSM is not inited");
+        super("FSM is not initialized");
     }
 }

src/test/java/me/bvn13/fsm/tests/FsmTest.java

@@ -109,11 +109,9 @@ public class FsmTest {
                     .to("finish")
                     .checking((fsm, event) -> true)
                 .end()
-                .create()
-                ;
+                .create();
 
         // @formatter:on
-
         simpleFsm.process("");
         simpleFsm.process("");
 
@@ -127,4 +125,67 @@ public class FsmTest {
 
     }
 
+    @Test
+    public void newSyntaxCustomState() {
+
+        AtomicBoolean initBefore = new AtomicBoolean(false);
+        AtomicBoolean initAfter = new AtomicBoolean(false);
+        AtomicBoolean initProcess = new AtomicBoolean(false);
+        AtomicBoolean intermediateBefore = new AtomicBoolean(false);
+        AtomicBoolean intermediateAfter = new AtomicBoolean(false);
+        AtomicBoolean intermediateProcess = new AtomicBoolean(false);
+        AtomicBoolean finishBefore = new AtomicBoolean(false);
+        AtomicBoolean finishAfter = new AtomicBoolean(false);
+        AtomicBoolean finishProcess = new AtomicBoolean(false);
+
+        // @formatter:off
+
+        SimpleFsm<String> simpleFsm = Fsm
+                .<SimpleFsm<String>, String>from(SimpleFsm::new)
+                .withStates()
+                .from("init")
+                    .withBeforeHandler(fsm -> initBefore.set(true))
+                    .withAfterHandler(fsm -> initAfter.set(true))
+                    .withProcessor((fsm, event) -> initProcess.set(true))
+                .end()
+                .state("intermediate")
+                    .withBeforeHandler(fsm -> intermediateBefore.set(true))
+                    .withAfterHandler(fsm -> intermediateAfter.set(true))
+                    .withProcessor((fsm, event) -> intermediateProcess.set(true))
+                .end()
+                .finish("finish")
+                    .withBeforeHandler(fsm -> finishBefore.set(true))
+                    .withAfterHandler(fsm -> finishAfter.set(true))
+                    .withProcessor((fsm, event) -> finishProcess.set(true))
+                .end()
+                .withTransition()
+                    .from("init")
+                    .to("intermediate")
+                    .checking((fsm, event) -> true)
+                .end()
+                .withTransition()
+                    .from("intermediate")
+                    .to("finish")
+                    .checking((fsm, event) -> true)
+                .end()
+                .startingAt("intermediate")
+                ;
+
+        // @formatter:on
+
+        simpleFsm.process("");
+
+        Assert.assertEquals("finish", simpleFsm.getCurrentState().getName());
+        Assert.assertFalse(initBefore.get());
+        Assert.assertFalse(initProcess.get());
+        Assert.assertFalse(initAfter.get());
+        Assert.assertTrue(intermediateBefore.get());
+        Assert.assertTrue(intermediateAfter.get());
+        Assert.assertTrue(intermediateProcess.get());
+        Assert.assertTrue(finishBefore.get());
+        Assert.assertFalse(finishProcess.get());
+        Assert.assertFalse(finishAfter.get());
+
+    }
+
 }