From 2f0029a04056a19359ed4336273f1a3a790f4c50 Mon Sep 17 00:00:00 2001
From: Sam Harwell <sam@tunnelvisionlabs.com>
Date: Wed, 18 Jul 2012 15:04:05 -0500
Subject: [PATCH] Improved handling of (potentially) null fields

---
 .../Java/src/org/antlr/v4/runtime/DefaultErrorStrategy.java   | 3 ++-
 runtime/Java/src/org/antlr/v4/runtime/Lexer.java              | 4 ++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/runtime/Java/src/org/antlr/v4/runtime/DefaultErrorStrategy.java b/runtime/Java/src/org/antlr/v4/runtime/DefaultErrorStrategy.java
index fe47fc69a..dad26c7e5 100644
--- a/runtime/Java/src/org/antlr/v4/runtime/DefaultErrorStrategy.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/DefaultErrorStrategy.java
@@ -126,7 +126,8 @@ public class DefaultErrorStrategy implements ANTLRErrorStrategy {
 //						   lastErrorIndex+
 //						   ", states="+lastErrorStates);
 		if ( lastErrorIndex==recognizer.getInputStream().index() &&
-		lastErrorStates.contains(recognizer._ctx.s) ) {
+			lastErrorStates != null &&
+			lastErrorStates.contains(recognizer._ctx.s) ) {
 			// uh oh, another error at same token index and previously-visited
 			// state in ATN; must be a case where LT(1) is in the recovery
 			// token set so nothing got consumed. Consume a single token
diff --git a/runtime/Java/src/org/antlr/v4/runtime/Lexer.java b/runtime/Java/src/org/antlr/v4/runtime/Lexer.java
index b8dd57863..34b2fe426 100644
--- a/runtime/Java/src/org/antlr/v4/runtime/Lexer.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/Lexer.java
@@ -130,6 +130,10 @@ public abstract class Lexer extends Recognizer<Integer, LexerATNSimulator>
 	 */
 	@Override
 	public Token nextToken() {
+		if (_input == null) {
+			throw new IllegalStateException("nextToken requires a non-null input stream.");
+		}
+
 		if (_hitEOF) {
 			emitEOF();
 			return _token;