diff --git a/runtime/Java/src/org/antlr/v4/runtime/DefaultErrorStrategy.java b/runtime/Java/src/org/antlr/v4/runtime/DefaultErrorStrategy.java
index 464f10769..d3eed2a0a 100644
--- a/runtime/Java/src/org/antlr/v4/runtime/DefaultErrorStrategy.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/DefaultErrorStrategy.java
@@ -205,8 +205,8 @@ public class DefaultErrorStrategy implements ANTLRErrorStrategy {
 		TokenStream tokens = recognizer.getInputStream();
 		String input;
 		if (tokens instanceof TokenStream) {
-			if ( e.startToken.getType()==Token.EOF ) input = "<EOF>";
-			else input = ((TokenStream)tokens).getText(e.startToken, e.offendingToken);
+			if ( e.getStartToken().getType()==Token.EOF ) input = "<EOF>";
+			else input = ((TokenStream)tokens).getText(e.getStartToken(), e.offendingToken);
 		}
 		else {
 			input = "<unknown input>";
diff --git a/runtime/Java/src/org/antlr/v4/runtime/LexerNoViableAltException.java b/runtime/Java/src/org/antlr/v4/runtime/LexerNoViableAltException.java
index b3a971ce9..6c01c18ee 100644
--- a/runtime/Java/src/org/antlr/v4/runtime/LexerNoViableAltException.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/LexerNoViableAltException.java
@@ -31,24 +31,36 @@ package org.antlr.v4.runtime;
 
 import org.antlr.v4.runtime.atn.ATNConfigSet;
 import org.antlr.v4.runtime.misc.Interval;
+import org.antlr.v4.runtime.misc.NotNull;
+import org.antlr.v4.runtime.misc.Nullable;
 import org.antlr.v4.runtime.misc.Utils;
 
 public class LexerNoViableAltException extends RecognitionException {
 	/** Matching attempted at what input index? */
-	public int startIndex;
+	private final int startIndex;
 
 	/** Which configurations did we try at input.index() that couldn't match input.LA(1)? */
-	public ATNConfigSet deadEndConfigs;
+	@Nullable
+	private final ATNConfigSet deadEndConfigs;
 
-	public LexerNoViableAltException(Lexer lexer,
-									 CharStream input,
+	public LexerNoViableAltException(@Nullable Lexer lexer,
+									 @NotNull CharStream input,
 									 int startIndex,
-									 ATNConfigSet deadEndConfigs) {
+									 @Nullable ATNConfigSet deadEndConfigs) {
 		super(lexer, input, null);
 		this.startIndex = startIndex;
 		this.deadEndConfigs = deadEndConfigs;
 	}
 
+	public int getStartIndex() {
+		return startIndex;
+	}
+
+	@Nullable
+	public ATNConfigSet getDeadEndConfigs() {
+		return deadEndConfigs;
+	}
+
 	@Override
 	public CharStream getInputStream() {
 		return (CharStream)super.getInputStream();
@@ -62,6 +74,6 @@ public class LexerNoViableAltException extends RecognitionException {
 			symbol = Utils.escapeWhitespace(symbol, false);
 		}
 
-		return "NoViableAltException('" + symbol + "')";
+		return String.format("%s('%s')", LexerNoViableAltException.class.getSimpleName(), symbol);
 	}
 }
diff --git a/runtime/Java/src/org/antlr/v4/runtime/NoViableAltException.java b/runtime/Java/src/org/antlr/v4/runtime/NoViableAltException.java
index a43784ef8..2403fe7f9 100644
--- a/runtime/Java/src/org/antlr/v4/runtime/NoViableAltException.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/NoViableAltException.java
@@ -29,6 +29,8 @@
 package org.antlr.v4.runtime;
 
 import org.antlr.v4.runtime.atn.ATNConfigSet;
+import org.antlr.v4.runtime.misc.NotNull;
+import org.antlr.v4.runtime.misc.Nullable;
 
 /** Indicates that the parser could not decide which of two or more paths
  *  to take based upon the remaining input. It tracks the starting token
@@ -37,33 +39,47 @@ import org.antlr.v4.runtime.atn.ATNConfigSet;
  */
 public class NoViableAltException extends RecognitionException {
 	/** Which configurations did we try at input.index() that couldn't match input.LT(1)? */
-	public ATNConfigSet deadEndConfigs;
+	@Nullable
+	private final ATNConfigSet deadEndConfigs;
 
 	/** The token object at the start index; the input stream might
 	 * 	not be buffering tokens so get a reference to it. (At the
 	 *  time the error occurred, of course the stream needs to keep a
 	 *  buffer all of the tokens but later we might not have access to those.)
 	 */
-	public Token startToken;
+	@NotNull
+	private final Token startToken;
 
-	public NoViableAltException(Parser recognizer) { // LL(1) error
-		this(recognizer,recognizer.getInputStream(),
+	public NoViableAltException(@NotNull Parser recognizer) { // LL(1) error
+		this(recognizer,
+			 recognizer.getInputStream(),
 			 recognizer.getCurrentToken(),
 			 recognizer.getCurrentToken(),
 			 null,
 			 recognizer._ctx);
 	}
 
-	public NoViableAltException(Parser recognizer,
-								TokenStream input,
-								Token startToken,
-								Token offendingToken,
-								ATNConfigSet deadEndConfigs,
-								ParserRuleContext<?> ctx)
+	public NoViableAltException(@NotNull Parser recognizer,
+								@NotNull TokenStream input,
+								@NotNull Token startToken,
+								@NotNull Token offendingToken,
+								@Nullable ATNConfigSet deadEndConfigs,
+								@NotNull ParserRuleContext<?> ctx)
 	{
 		super(recognizer, input, ctx);
 		this.deadEndConfigs = deadEndConfigs;
 		this.startToken = startToken;
 		this.offendingToken = offendingToken;
 	}
+
+	@NotNull
+	public Token getStartToken() {
+		return startToken;
+	}
+
+	@Nullable
+	public ATNConfigSet getDeadEndConfigs() {
+		return deadEndConfigs;
+	}
+
 }
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 ca470e926..a5b51e2d3 100755
--- a/runtime/Java/src/org/antlr/v4/runtime/atn/ParserATNSimulator.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/atn/ParserATNSimulator.java
@@ -1368,7 +1368,7 @@ public class ParserATNSimulator extends ATNSimulator {
 
 	public void dumpDeadEndConfigs(@NotNull NoViableAltException nvae) {
 		System.err.println("dead end configs: ");
-		for (ATNConfig c : nvae.deadEndConfigs) {
+		for (ATNConfig c : nvae.getDeadEndConfigs()) {
 			String trans = "no edges";
 			if ( c.state.getNumberOfTransitions()>0 ) {
 				Transition t = c.state.transition(0);