diff --git a/tool/src/org/antlr/v4/automata/ATNSerializer.java b/tool/src/org/antlr/v4/automata/ATNSerializer.java
index 5d727854b..bb3fa6653 100644
--- a/tool/src/org/antlr/v4/automata/ATNSerializer.java
+++ b/tool/src/org/antlr/v4/automata/ATNSerializer.java
@@ -32,6 +32,7 @@ package org.antlr.v4.automata;
 import org.antlr.v4.misc.Utils;
 import org.antlr.v4.parse.ANTLRParser;
 import org.antlr.v4.runtime.atn.*;
+import org.antlr.v4.runtime.misc.IntegerList;
 import org.antlr.v4.runtime.misc.Interval;
 import org.antlr.v4.runtime.misc.IntervalSet;
 import org.antlr.v4.tool.Grammar;
@@ -71,8 +72,8 @@ public class ATNSerializer {
 	 *
 	 *  Convenient to pack into unsigned shorts to make as Java string.
 	 */
-	public List<Integer> serialize() {
-		List<Integer> data = new ArrayList<Integer>();
+	public IntegerList serialize() {
+		IntegerList data = new IntegerList();
 		// convert grammar type to ATN const to avoid dependence on ANTLRParser
 		if ( g.getType()== ANTLRParser.LEXER ) data.add(ATN.LEXER);
 		else if ( g.getType()== ANTLRParser.PARSER ) data.add(ATN.PARSER);
@@ -277,7 +278,7 @@ public class ATNSerializer {
 		return new String(Utils.toCharArray(getSerialized(g, atn)));
 	}
 
-	public static List<Integer> getSerialized(Grammar g, ATN atn) {
+	public static IntegerList getSerialized(Grammar g, ATN atn) {
 		return new ATNSerializer(g, atn).serialize();
 	}
 
@@ -286,7 +287,7 @@ public class ATNSerializer {
 	}
 
 	public static String getDecoded(Grammar g, ATN atn) {
-		List<Integer> serialized = getSerialized(g, atn);
+		IntegerList serialized = getSerialized(g, atn);
 		char[] data = Utils.toCharArray(serialized);
 		return new ATNSerializer(g, atn).decode(data);
 	}
diff --git a/tool/src/org/antlr/v4/codegen/model/SerializedATN.java b/tool/src/org/antlr/v4/codegen/model/SerializedATN.java
index c8706a76d..e58c3c511 100644
--- a/tool/src/org/antlr/v4/codegen/model/SerializedATN.java
+++ b/tool/src/org/antlr/v4/codegen/model/SerializedATN.java
@@ -32,6 +32,7 @@ package org.antlr.v4.codegen.model;
 import org.antlr.v4.automata.ATNSerializer;
 import org.antlr.v4.codegen.OutputModelFactory;
 import org.antlr.v4.runtime.atn.ATN;
+import org.antlr.v4.runtime.misc.IntegerList;
 
 import java.util.*;
 
@@ -40,9 +41,9 @@ public class SerializedATN extends OutputModelObject {
 	public List<String> serialized;
 	public SerializedATN(OutputModelFactory factory, ATN atn) {
 		super(factory);
-		List<Integer> data = ATNSerializer.getSerialized(factory.getGrammar(), atn);
+		IntegerList data = ATNSerializer.getSerialized(factory.getGrammar(), atn);
 		serialized = new ArrayList<String>(data.size());
-		for (int c : data) {
+		for (int c : data.toArray()) {
 			String encoded = factory.getGenerator().target.encodeIntAsCharEscape(c == -1 ? Character.MAX_VALUE : c);
 			serialized.add(encoded);
 		}
diff --git a/tool/src/org/antlr/v4/misc/Utils.java b/tool/src/org/antlr/v4/misc/Utils.java
index 7dd29e7dc..3006d7da0 100644
--- a/tool/src/org/antlr/v4/misc/Utils.java
+++ b/tool/src/org/antlr/v4/misc/Utils.java
@@ -29,6 +29,7 @@
 
 package org.antlr.v4.misc;
 
+import org.antlr.v4.runtime.misc.IntegerList;
 import org.antlr.v4.tool.ast.GrammarAST;
 
 import java.util.*;
@@ -137,13 +138,6 @@ public class Utils {
 //		return x;
 //	}
 
-	public static int[] toIntArray(List<Integer> list) {
-		if ( list==null ) return null;
-		int[] a = new int[list.size()];
-		for (int i=0; i<list.size(); i++) a[i] = list.get(i);
-		return a;
-	}
-
 	public static String capitalize(String s) {
 		return Character.toUpperCase(s.charAt(0)) + s.substring(1);
 	}
@@ -152,11 +146,11 @@ public class Utils {
 		return Character.toLowerCase(s.charAt(0)) + s.substring(1);
 	}
 
-	public static char[] toCharArray(List<Integer> data) {
+	public static char[] toCharArray(IntegerList data) {
 		if ( data==null ) return null;
 		char[] cdata = new char[data.size()];
 		for (int i=0; i<data.size(); i++) {
-			cdata[i] = (char)(int)data.get(i);
+			cdata[i] = (char)data.get(i);
 		}
 		return cdata;
 	}
diff --git a/tool/src/org/antlr/v4/tool/DOTGenerator.java b/tool/src/org/antlr/v4/tool/DOTGenerator.java
index c8d651563..75779e8a8 100644
--- a/tool/src/org/antlr/v4/tool/DOTGenerator.java
+++ b/tool/src/org/antlr/v4/tool/DOTGenerator.java
@@ -33,6 +33,7 @@ import org.antlr.v4.misc.Utils;
 import org.antlr.v4.runtime.atn.*;
 import org.antlr.v4.runtime.dfa.DFA;
 import org.antlr.v4.runtime.dfa.DFAState;
+import org.antlr.v4.runtime.misc.IntegerList;
 import org.stringtemplate.v4.ST;
 import org.stringtemplate.v4.STGroup;
 import org.stringtemplate.v4.STGroupDir;
@@ -120,9 +121,9 @@ public class DOTGenerator {
 			if ( alts!=null ) {
 				buf.append("\\n");
 				// separate alts
-				List<Integer> altList = new ArrayList<Integer>();
+				IntegerList altList = new IntegerList();
 				altList.addAll(alts);
-				Collections.sort(altList);
+				altList.sort();
 				Set<ATNConfig> configurations = s.configset;
 				for (int altIndex = 0; altIndex < altList.size(); altIndex++) {
 					int alt = altList.get(altIndex);
diff --git a/tool/src/org/antlr/v4/tool/Grammar.java b/tool/src/org/antlr/v4/tool/Grammar.java
index 7a644f7c5..27540169e 100644
--- a/tool/src/org/antlr/v4/tool/Grammar.java
+++ b/tool/src/org/antlr/v4/tool/Grammar.java
@@ -46,6 +46,7 @@ import org.antlr.v4.runtime.Token;
 import org.antlr.v4.runtime.atn.ATN;
 import org.antlr.v4.runtime.dfa.DFA;
 import org.antlr.v4.runtime.misc.IntSet;
+import org.antlr.v4.runtime.misc.IntegerList;
 import org.antlr.v4.runtime.misc.IntervalSet;
 import org.antlr.v4.runtime.misc.NotNull;
 import org.antlr.v4.runtime.misc.Nullable;
@@ -58,7 +59,6 @@ import org.antlr.v4.tool.ast.TerminalAST;
 
 import java.io.IOException;
 import java.util.ArrayList;
-import java.util.Collection;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedHashMap;
@@ -466,9 +466,9 @@ public class Grammar implements AttributeResolver {
 		return tokenName;
 	}
 
-	public List<String> getTokenDisplayNames(Collection<Integer> types) {
+	public List<String> getTokenDisplayNames(IntegerList types) {
 		List<String> names = new ArrayList<String>();
-		for (int t : types) names.add(getTokenDisplayName(t));
+		for (int t : types.toArray()) names.add(getTokenDisplayName(t));
 		return names;
 	}
 
diff --git a/tool/test/org/antlr/v4/test/BaseTest.java b/tool/test/org/antlr/v4/test/BaseTest.java
index 8009a1254..ad6c7e13f 100644
--- a/tool/test/org/antlr/v4/test/BaseTest.java
+++ b/tool/test/org/antlr/v4/test/BaseTest.java
@@ -50,6 +50,7 @@ import org.antlr.v4.runtime.atn.ATNState;
 import org.antlr.v4.runtime.atn.DecisionState;
 import org.antlr.v4.runtime.atn.LexerATNSimulator;
 import org.antlr.v4.runtime.dfa.DFA;
+import org.antlr.v4.runtime.misc.IntegerList;
 import org.antlr.v4.runtime.misc.Interval;
 import org.antlr.v4.runtime.misc.Nullable;
 import org.antlr.v4.semantics.SemanticPipeline;
@@ -184,8 +185,8 @@ public abstract class BaseTest {
 //		dfa.minimized = dmin.minimize();
 //	}
 
-	List<Integer> getTypesFromString(Grammar g, String expecting) {
-		List<Integer> expectingTokenTypes = new ArrayList<Integer>();
+	IntegerList getTypesFromString(Grammar g, String expecting) {
+		IntegerList expectingTokenTypes = new IntegerList();
 		if ( expecting!=null && !expecting.trim().isEmpty() ) {
 			for (String tname : expecting.replace(" ", "").split(",")) {
 				int ttype = g.getTokenType(tname);
@@ -195,9 +196,9 @@ public abstract class BaseTest {
 		return expectingTokenTypes;
 	}
 
-	public List<Integer> getTokenTypesViaATN(String input, LexerATNSimulator lexerATN) {
+	public IntegerList getTokenTypesViaATN(String input, LexerATNSimulator lexerATN) {
 		ANTLRInputStream in = new ANTLRInputStream(input);
-		List<Integer> tokenTypes = new ArrayList<Integer>();
+		IntegerList tokenTypes = new IntegerList();
 		int ttype;
 		do {
 			ttype = lexerATN.matchATN(in);
@@ -1065,9 +1066,9 @@ public abstract class BaseTest {
     public void assertNull(Object object) { try {Assert.assertNull(object);} catch (Error e) {lastTestFailed=true; throw e;} }
 
 	public static class IntTokenStream implements TokenStream {
-		List<Integer> types;
+		IntegerList types;
 		int p=0;
-		public IntTokenStream(List<Integer> types) { this.types = types; }
+		public IntTokenStream(IntegerList types) { this.types = types; }
 
 		@Override
 		public void consume() { p++; }
diff --git a/tool/test/org/antlr/v4/test/TestATNInterpreter.java b/tool/test/org/antlr/v4/test/TestATNInterpreter.java
index f7c120430..32fab5105 100644
--- a/tool/test/org/antlr/v4/test/TestATNInterpreter.java
+++ b/tool/test/org/antlr/v4/test/TestATNInterpreter.java
@@ -7,6 +7,7 @@ import org.antlr.v4.runtime.atn.ATN;
 import org.antlr.v4.runtime.atn.ATNState;
 import org.antlr.v4.runtime.atn.BlockStartState;
 import org.antlr.v4.runtime.atn.LexerATNSimulator;
+import org.antlr.v4.runtime.misc.IntegerList;
 import org.antlr.v4.tool.DOTGenerator;
 import org.antlr.v4.tool.Grammar;
 import org.antlr.v4.tool.LexerGrammar;
@@ -14,9 +15,6 @@ import org.antlr.v4.tool.Rule;
 import org.antlr.v4.tool.interp.ParserInterpreter;
 import org.junit.Test;
 
-import java.util.List;
-
-
 	// NOTICE: TOKENS IN LEXER, PARSER MUST BE SAME OR TOKEN TYPE MISMATCH
 	// NOTICE: TOKENS IN LEXER, PARSER MUST BE SAME OR TOKEN TYPE MISMATCH
 	// NOTICE: TOKENS IN LEXER, PARSER MUST BE SAME OR TOKEN TYPE MISMATCH
@@ -275,7 +273,7 @@ public class TestATNInterpreter extends BaseTest {
 	{
 		ATN lexatn = createATN(lg);
 		LexerATNSimulator lexInterp = new LexerATNSimulator(lexatn);
-		List<Integer> types = getTokenTypesViaATN(inputString, lexInterp);
+		IntegerList types = getTokenTypesViaATN(inputString, lexInterp);
 		System.out.println(types);
 
 		semanticProcess(lg);
diff --git a/tool/test/org/antlr/v4/test/TestATNParserPrediction.java b/tool/test/org/antlr/v4/test/TestATNParserPrediction.java
index 4393a5a1b..9ef7c684b 100644
--- a/tool/test/org/antlr/v4/test/TestATNParserPrediction.java
+++ b/tool/test/org/antlr/v4/test/TestATNParserPrediction.java
@@ -37,6 +37,7 @@ import org.antlr.v4.runtime.Token;
 import org.antlr.v4.runtime.TokenStream;
 import org.antlr.v4.runtime.atn.*;
 import org.antlr.v4.runtime.dfa.DFA;
+import org.antlr.v4.runtime.misc.IntegerList;
 import org.antlr.v4.tool.DOTGenerator;
 import org.antlr.v4.tool.Grammar;
 import org.antlr.v4.tool.LexerGrammar;
@@ -44,8 +45,6 @@ import org.antlr.v4.tool.Rule;
 import org.antlr.v4.tool.interp.ParserInterpreter;
 import org.junit.Test;
 
-import java.util.List;
-
 	// NOTICE: TOKENS IN LEXER, PARSER MUST BE SAME OR TOKEN TYPE MISMATCH
 	// NOTICE: TOKENS IN LEXER, PARSER MUST BE SAME OR TOKEN TYPE MISMATCH
 	// NOTICE: TOKENS IN LEXER, PARSER MUST BE SAME OR TOKEN TYPE MISMATCH
@@ -477,7 +476,7 @@ public class TestATNParserPrediction extends BaseTest {
 		Tool.internalOption_ShowATNConfigsInDFA = true;
 		ATN lexatn = createATN(lg);
 		LexerATNSimulator lexInterp = new LexerATNSimulator(lexatn);
-		List<Integer> types = getTokenTypesViaATN(inputString, lexInterp);
+		IntegerList types = getTokenTypesViaATN(inputString, lexInterp);
 		System.out.println(types);
 
 		semanticProcess(lg);
@@ -542,7 +541,7 @@ public class TestATNParserPrediction extends BaseTest {
 //		System.out.println(dot.getDOT(atn.ruleToStartState.get(g.getRule("e"))));
 
 		ParserATNSimulator<Token> interp = new ParserATNSimulator<Token>(atn);
-		List<Integer> types = getTokenTypesViaATN(inputString, lexInterp);
+		IntegerList types = getTokenTypesViaATN(inputString, lexInterp);
 		System.out.println(types);
 		TokenStream input = new IntTokenStream(types);
 		try {
@@ -572,7 +571,7 @@ public class TestATNParserPrediction extends BaseTest {
 		ParserInterpreter interp = new ParserInterpreter(g, null);
 		for (int i=0; i<inputString.length; i++) {
 			// Check DFA
-			List<Integer> types = getTokenTypesViaATN(inputString[i], lexInterp);
+			IntegerList types = getTokenTypesViaATN(inputString[i], lexInterp);
 			System.out.println(types);
 			TokenStream input = new IntTokenStream(types);
 			try {