Initialize the elements of the decisionToDFA arrays when the array is created

runtime/Java/src/org/antlr/v4/runtime/Parser.java

@@ -751,7 +751,7 @@ public abstract class Parser extends Recognizer<Token, ParserATNSimulator> {
 			boolean seenOne = false;
 			for (int d = 0; d < _interp.decisionToDFA.length; d++) {
 				DFA dfa = _interp.decisionToDFA[d];
-				if ( dfa!=null ) {
+				if ( !dfa.states.isEmpty() ) {
 					if ( seenOne ) System.out.println();
 					System.out.println("Decision " + dfa.decision + ":");
 					System.out.print(dfa.toString(getTokenNames()));

runtime/Java/src/org/antlr/v4/runtime/atn/LexerATNSimulator.java

@@ -119,15 +119,6 @@ public class LexerATNSimulator extends ATNSimulator {
 	{
 		super(atn,sharedContextCache);
 		this.decisionToDFA = decisionToDFA;
-		if ( decisionToDFA[Lexer.DEFAULT_MODE]==null ) { // create all mode dfa
-			synchronized (this.decisionToDFA) {
-				if ( decisionToDFA[Lexer.DEFAULT_MODE]==null ) { // create all mode dfa
-					for (int i=0; i<atn.modeToStartState.size(); i++) {
-						this.decisionToDFA[i] = new DFA(atn.modeToStartState.get(i));
-					}
-				}
-			}
-		}
 		this.recog = recog;
 	}
 

runtime/Java/src/org/antlr/v4/runtime/atn/ParserATNSimulator.java

@@ -325,18 +325,7 @@ public class ParserATNSimulator extends ATNSimulator {
 		_outerContext = outerContext;
 		predict_calls++;
 		DFA dfa = decisionToDFA[decision];
-		// First, synchronize on the array of DFA for this parser
+
-		// so that we can get the DFA for a decision or create and set one
-		if ( dfa==null ) { // only create one if not there
-			synchronized (decisionToDFA) {
-				dfa = decisionToDFA[decision];
-				if ( dfa==null ) { // the usual double-check
-					DecisionState startState = atn.decisionToState.get(decision);
-					decisionToDFA[decision] = new DFA(startState, decision);
-					dfa = decisionToDFA[decision];
-				}
-			}
-		}
 		// Now we are certain to have a specific decision's DFA
 		// But, do we still need an initial state?
 		if ( dfa.s0==null ) { // recheck

tool/resources/org/antlr/v4/tool/templates/codegen/Java/Java.stg

@@ -838,6 +838,9 @@ public static final ATN _ATN =
 	ATNSimulator.deserialize(_serializedATN.toCharArray());
 static {
 	_decisionToDFA = new DFA[_ATN.getNumberOfDecisions()];
+	for (int i = 0; i \< _ATN.getNumberOfDecisions(); i++) {
+		_decisionToDFA[i] = new DFA(_ATN.getDecisionState(i), i);
+	}
 <!	org.antlr.v4.tool.DOTGenerator dot = new org.antlr.v4.tool.DOTGenerator(null);!>
 <!	System.out.println(dot.getDOT(_ATN.decisionToState.get(0), ruleNames, false));!>
 <!	System.out.println(dot.getDOT(_ATN.ruleToStartState[2], ruleNames, false));!>

tool/src/org/antlr/v4/tool/interp/LexerInterpreter.java

@@ -53,7 +53,7 @@ public class LexerInterpreter implements TokenSource {
 	/** How to create token objects */
 	protected TokenFactory<?> _factory = CommonTokenFactory.DEFAULT;
 
-	protected final DFA[] _decisionToDFA = new DFA[1];
+	protected final DFA[] _decisionToDFA;
 	protected final PredictionContextCache _sharedContextCache =
 		new PredictionContextCache();
 
@@ -65,6 +65,10 @@ public class LexerInterpreter implements TokenSource {
 	public LexerInterpreter(LexerGrammar g) {
 		Tool antlr = new Tool();
 		antlr.process(g,false);
+		_decisionToDFA = new DFA[g.atn.getNumberOfDecisions()];
+		for (int i = 0; i < _decisionToDFA.length; i++) {
+			_decisionToDFA[i] = new DFA(g.atn.getDecisionState(i), i);
+		}
 		interp = new LexerATNSimulator(g.atn,_decisionToDFA,_sharedContextCache);
 	}
 

tool/src/org/antlr/v4/tool/interp/ParserInterpreter.java

@@ -46,15 +46,20 @@ import org.antlr.v4.tool.Grammar;
 
 public class ParserInterpreter {
 	public static class DummyParser extends Parser {
+		public final ATN atn;
 		public final DFA[] decisionToDFA; // not shared for interp
 		public final PredictionContextCache sharedContextCache =
 			new PredictionContextCache();
 
 		public Grammar g;
-		public DummyParser(Grammar g, TokenStream input) {
+		public DummyParser(Grammar g, ATN atn, TokenStream input) {
 			super(input);
 			this.g = g;
-			decisionToDFA = new DFA[100];
+			this.atn = atn;
+			this.decisionToDFA = new DFA[atn.getNumberOfDecisions()];
+			for (int i = 0; i < decisionToDFA.length; i++) {
+				decisionToDFA[i] = new DFA(atn.getDecisionState(i), i);
+			}
 		}
 
 		@Override
@@ -74,9 +79,7 @@ public class ParserInterpreter {
 
 		@Override
 		public ATN getATN() {
-			return null;
+			return atn;
-		}
-		static {
 		}
 	}
 
@@ -92,7 +95,7 @@ public class ParserInterpreter {
 	public ParserInterpreter(@NotNull Grammar g, @NotNull TokenStream input) {
 		Tool antlr = new Tool();
 		antlr.process(g,false);
-		parser = new DummyParser(g, input);
+		parser = new DummyParser(g, g.atn, input);
 		atnSimulator =
 			new ParserATNSimulator(parser, g.atn, parser.decisionToDFA,
 										  parser.sharedContextCache);

tool/test/org/antlr/v4/test/BaseTest.java

@@ -236,7 +236,7 @@ public abstract class BaseTest {
 									  ATN atn,
 									  CharStream input)
 	{
-		LexerATNSimulator interp = new LexerATNSimulator(atn,new DFA[1],null);
+		LexerATNSimulator interp = new LexerATNSimulator(atn,new DFA[] { new DFA(atn.modeToStartState.get(Lexer.DEFAULT_MODE)) },null);
 		List<String> tokenTypes = new ArrayList<String>();
 		int ttype;
 		boolean hitEOF = false;

tool/test/org/antlr/v4/test/TestATNInterpreter.java

@@ -31,6 +31,7 @@
 package org.antlr.v4.test;
 
 import org.antlr.v4.automata.ParserATNFactory;
+import org.antlr.v4.runtime.Lexer;
 import org.antlr.v4.runtime.NoViableAltException;
 import org.antlr.v4.runtime.atn.ATN;
 import org.antlr.v4.runtime.atn.ATNState;
@@ -381,7 +382,7 @@ public class TestATNInterpreter extends BaseTest {
 								int expected)
 	{
 		ATN lexatn = createATN(lg, true);
-		LexerATNSimulator lexInterp = new LexerATNSimulator(lexatn,new DFA[1],null);
+		LexerATNSimulator lexInterp = new LexerATNSimulator(lexatn,new DFA[] { new DFA(lexatn.modeToStartState.get(Lexer.DEFAULT_MODE)) },null);
 		IntegerList types = getTokenTypesViaATN(inputString, lexInterp);
 		System.out.println(types);
 

tool/test/org/antlr/v4/test/TestATNParserPrediction.java

@@ -32,6 +32,7 @@ package org.antlr.v4.test;
 
 import org.antlr.v4.Tool;
 import org.antlr.v4.automata.ParserATNFactory;
+import org.antlr.v4.runtime.Lexer;
 import org.antlr.v4.runtime.NoViableAltException;
 import org.antlr.v4.runtime.ParserRuleContext;
 import org.antlr.v4.runtime.TokenStream;
@@ -460,7 +461,7 @@ public class TestATNParserPrediction extends BaseTest {
 		Tool.internalOption_ShowATNConfigsInDFA = true;
 		ATN lexatn = createATN(lg, true);
 		LexerATNSimulator lexInterp =
-			new LexerATNSimulator(lexatn,new DFA[1],new PredictionContextCache());
+			new LexerATNSimulator(lexatn,new DFA[] { new DFA(lexatn.modeToStartState.get(Lexer.DEFAULT_MODE)) },new PredictionContextCache());
 		IntegerList types = getTokenTypesViaATN(inputString, lexInterp);
 		System.out.println(types);
 
@@ -550,7 +551,7 @@ public class TestATNParserPrediction extends BaseTest {
 //		Tool.internalOption_ShowATNConfigsInDFA = true;
 		ATN lexatn = createATN(lg, true);
 		LexerATNSimulator lexInterp =
-			new LexerATNSimulator(lexatn,new DFA[1], new PredictionContextCache());
+			new LexerATNSimulator(lexatn,new DFA[] { new DFA(lexatn.getDecisionState(Lexer.DEFAULT_MODE)) }, new PredictionContextCache());
 
 		semanticProcess(lg);
 		g.importVocab(lg);