Issue #10 make sure that State emits a specific match only once

src/main/java/org/ahocorasick/trie/State.java

@@ -41,7 +41,7 @@ public class State {
     private State failure = null;
 
     /** whenever this state is reached, it will emit the matches keywords for future reference */
-    private List<String> emits = null;
+    private Set<String> emits = null;
 
     public State() {
         this(0);
@@ -83,7 +83,7 @@ public class State {
 
     public void addEmit(String keyword) {
         if (this.emits == null) {
-            this.emits = new ArrayList<String>();
+            this.emits = new TreeSet<>();
         }
         this.emits.add(keyword);
     }

src/test/java/org/ahocorasick/trie/TrieTest.java

@@ -48,8 +48,8 @@ public class TrieTest {
         Collection<Emit> emits = trie.parseText("ushers");
         assertEquals(3, emits.size()); // she @ 3, he @ 3, hers @ 5
         Iterator<Emit> iterator = emits.iterator();
-        checkEmit(iterator.next(), 1, 3, "she");
         checkEmit(iterator.next(), 2, 3, "he");
+        checkEmit(iterator.next(), 1, 3, "she");
         checkEmit(iterator.next(), 2, 5, "hers");
     }
 
@@ -87,10 +87,10 @@ public class TrieTest {
         checkEmit(iterator.next(), 0, 1, "he");
         checkEmit(iterator.next(), 2, 3, "he");
         checkEmit(iterator.next(), 4, 5, "he");
-        checkEmit(iterator.next(), 0, 7, "hehehehe");
         checkEmit(iterator.next(), 6, 7, "he");
-        checkEmit(iterator.next(), 2, 9, "hehehehe");
+        checkEmit(iterator.next(), 0, 7, "hehehehe");
         checkEmit(iterator.next(), 8, 9, "he");
+        checkEmit(iterator.next(), 2, 9, "hehehehe");
     }
 
     @Test