From 979bd13725b0f7887c40ce8cb84c8d4eb1f37d56 Mon Sep 17 00:00:00 2001
From: dingxin-tech <453127511@qq.com>
Date: Tue, 3 Jun 2025 14:10:07 +0800
Subject: [PATCH] perf(runtime): Optimize thread safety and performance for DFA
 state management

Signed-off-by: dingxin-tech <453127511@qq.com>
---
 .../v4/runtime/atn/LexerATNSimulator.java     | 19 ++++++-------
 .../v4/runtime/atn/ParserATNSimulator.java    | 28 +++++++++----------
 .../src/org/antlr/v4/runtime/dfa/DFA.java     |  4 +--
 3 files changed, 24 insertions(+), 27 deletions(-)

diff --git a/runtime/Java/src/org/antlr/v4/runtime/atn/LexerATNSimulator.java b/runtime/Java/src/org/antlr/v4/runtime/atn/LexerATNSimulator.java
index 254e17839b..219ffe6f71 100644
--- a/runtime/Java/src/org/antlr/v4/runtime/atn/LexerATNSimulator.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/atn/LexerATNSimulator.java
@@ -687,18 +687,17 @@ protected DFAState addDFAState(ATNConfigSet configs) {
 		}
 
 		DFA dfa = decisionToDFA[mode];
-		synchronized (dfa.states) {
-			DFAState existing = dfa.states.get(proposed);
-			if ( existing!=null ) return existing;
 
-			DFAState newState = proposed;
+		DFAState existing = dfa.states.get(proposed);
+		if ( existing!=null ) return existing;
 
-			newState.stateNumber = dfa.states.size();
-			configs.setReadonly(true);
-			newState.configs = configs;
-			dfa.states.put(newState, newState);
-			return newState;
-		}
+		DFAState newState = proposed;
+
+		newState.stateNumber = dfa.states.size();
+		configs.setReadonly(true);
+		newState.configs = configs;
+		dfa.states.put(newState, newState);
+		return newState;
 	}
 
 
diff --git a/runtime/Java/src/org/antlr/v4/runtime/atn/ParserATNSimulator.java b/runtime/Java/src/org/antlr/v4/runtime/atn/ParserATNSimulator.java
index 80b08993fa..7dd7430796 100755
--- a/runtime/Java/src/org/antlr/v4/runtime/atn/ParserATNSimulator.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/atn/ParserATNSimulator.java
@@ -2101,26 +2101,24 @@ protected DFAState addDFAState(DFA dfa, DFAState D) {
 			return D;
 		}
 
-		synchronized (dfa.states) {
-			DFAState existing = dfa.states.get(D);
+		DFAState existing = dfa.states.get(D);
 
-			if ( existing!=null ) {
-				if ( trace_atn_sim ) System.out.println("addDFAState " + D + " exists");
-				return existing;
-			}
+		if ( existing!=null ) {
+			if ( trace_atn_sim ) System.out.println("addDFAState " + D + " exists");
+			return existing;
+		}
 
-			D.stateNumber = dfa.states.size();
+		D.stateNumber = dfa.states.size();
 
-			if (!D.configs.isReadonly()) {
-				D.configs.optimizeConfigs(this);
-				D.configs.setReadonly(true);
-			}
+		if (!D.configs.isReadonly()) {
+			D.configs.optimizeConfigs(this);
+			D.configs.setReadonly(true);
+		}
 
-			if ( trace_atn_sim ) System.out.println("addDFAState new "+D);
+		if ( trace_atn_sim ) System.out.println("addDFAState new "+D);
 
-			dfa.states.put(D, D);
-			return D;
-		}
+		dfa.states.put(D, D);
+		return D;
 	}
 
 	protected void reportAttemptingFullContext(DFA dfa, BitSet conflictingAlts, ATNConfigSet configs, int startIndex, int stopIndex) {
diff --git a/runtime/Java/src/org/antlr/v4/runtime/dfa/DFA.java b/runtime/Java/src/org/antlr/v4/runtime/dfa/DFA.java
index 3c91daba8c..b1d7565b6f 100644
--- a/runtime/Java/src/org/antlr/v4/runtime/dfa/DFA.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/dfa/DFA.java
@@ -16,17 +16,17 @@
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.Comparator;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 
 public class DFA {
 	/** A set of all DFA states. Use {@link Map} so we can get old state back
 	 *  ({@link Set} only allows you to see if it's there).
      */
 
-	public final Map<DFAState, DFAState> states = new HashMap<DFAState, DFAState>();
+	public final Map<DFAState, DFAState> states = new ConcurrentHashMap<>();
 
 	public volatile DFAState s0;