fix：避免调用方 显示调用API 触发查找树 优化；并通过内置锁，避免因并行树优化 可能造成的不可预知结果 和 无效重复的 树优化操作

hutool-core/src/main/java/cn/hutool/core/text/dfa/Automaton.java

@@ -4,19 +4,33 @@ import java.util.*;
 
 /**
  * <p>
- *
  * 基于非确定性有穷自动机（NFA） 实现的多模匹配工具
+ * </p>
  *
  * @author renyp
  */
 public class Automaton {
+    /**
+     * AC树的根节点
+     */
     private final Node root;
+    /**
+     * 标记是否需要构建AC自动机，做树优化
+     */
+    private volatile boolean needBuildAC;
+
+    /**
+     * 内置锁，防止并发场景，并行建AC树，造成不可预知结果
+     */
+    private final Object lock;
 
     /**
      * 默认构造
      */
     public Automaton() {
         this.root = new Node();
+        this.needBuildAC = true;
+        this.lock = new Object();
     }
 
     /**
@@ -35,6 +49,7 @@ public class Automaton {
      * @param word 添加的新词
      */
     public void insert(String word) {
+        needBuildAC = true;
         Node p = root;
         for (char curr : word.toCharArray()) {
             int ind = curr;
@@ -61,7 +76,7 @@ public class Automaton {
     /**
      * 构建基于NFA模型的 AC自动机
      */
-	public void buildAc() {
+    private void buildAc() {
         Queue<Node> queue = new LinkedList<>();
         Node p = root;
         for (Integer key : p.next.keySet()) {
@@ -86,6 +101,7 @@ public class Automaton {
                 queue.offer(curr.next.get(key));
             }
         }
+        needBuildAC = false;
     }
 
     /**
@@ -100,6 +116,14 @@ public class Automaton {
      * @param isDensityMatch 是否密集匹配
      */
     public List<FoundWord> find(String text, boolean isDensityMatch) {
+        // double check，防止重复无用的 buildAC
+        if (needBuildAC) {
+            synchronized (lock) {
+                if (needBuildAC) {
+                    this.buildAc();
+                }
+            }
+        }
         List<FoundWord> ans = new ArrayList<>();
         Node p = root, k = null;
         for (int i = 0, len = text.length(); i < len; i++) {
@@ -131,9 +155,21 @@ public class Automaton {
 
     private static class Node {
 
+        /**
+         * 当前节点是否是一个单词的结尾
+         */
         boolean flag;
+        /**
+         * 指向 当前节点匹配失败应该跳转的下个节点
+         */
         Node fail;
+        /**
+         * 以当前节点结尾的单词
+         */
         String str;
+        /**
+         * 当前节点的子节点
+         */
         Map<Integer, Node> next;
 
         public Node() {

hutool-core/src/test/java/cn/hutool/core/text/dfa/AutomatonTest.java

@@ -17,7 +17,7 @@ public class AutomatonTest extends TestCase {
 		Automaton automaton = new Automaton();
 		WordTree wordTree = new WordTree();
 		automaton.insert("say", "her", "he", "she", "shr");
-		automaton.buildAc();
+//		automaton.buildAc();
 		wordTree.addWords("say", "her", "he", "she", "shr");
 
 		StopWatch stopWatch = new StopWatch();
@@ -51,7 +51,7 @@ public class AutomatonTest extends TestCase {
 		Automaton automaton = new Automaton();
 		WordTree wordTree = new WordTree();
 		automaton.insert("say", "her", "he", "she", "shr");
-		automaton.buildAc();
+//		automaton.buildAc();
 		wordTree.addWords("say", "her", "he", "she", "shr");
 
 		StopWatch stopWatch = new StopWatch();
@@ -84,7 +84,7 @@ public class AutomatonTest extends TestCase {
 		stopWatch.start("automaton_char_buid_find");
 		Automaton automatonLocal = new Automaton();
 		automatonLocal.insert("say", "her", "he", "she", "shr");
-		automatonLocal.buildAc();
+//		automatonLocal.buildAc();
 		List<FoundWord> ans1 = automatonLocal.find(input);
 		stopWatch.stop();
 		assertEquals("she,he,her,say", ans1.stream().map(FoundWord::getWord).collect(Collectors.joining(",")));
@@ -118,7 +118,7 @@ public class AutomatonTest extends TestCase {
 		stopWatch.start("automaton_cn_build_find");
 		Automaton automatonLocal = new Automaton();
 		automatonLocal.insert("赵", "赵啊", "赵啊三");
-		automatonLocal.buildAc();
+//		automatonLocal.buildAc();
 
 		final List<FoundWord> result = automatonLocal.find(input);
 		stopWatch.stop();
@@ -156,7 +156,7 @@ public class AutomatonTest extends TestCase {
 
 		Automaton automatonLocal = new Automaton();
 		automatonLocal.insert("赵", "赵啊", "赵啊三");
-		automatonLocal.buildAc();
+//		automatonLocal.buildAc();
 
 		stopWatch.start("automaton_cn_find");
 		final List<FoundWord> result = automatonLocal.find(input);
@@ -196,7 +196,7 @@ public class AutomatonTest extends TestCase {
 
 		Automaton automatonLocal = new Automaton();
 		automatonLocal.insert("赵", "赵啊", "赵啊三");
-		automatonLocal.buildAc();
+//		automatonLocal.buildAc();
 
 		stopWatch.start("automaton_cn_find_not_density");
 		final List<FoundWord> result = automatonLocal.find(input, false);