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 50756148b..a46aed91f 100644
--- a/runtime/Java/src/org/antlr/v4/runtime/atn/LexerATNSimulator.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/atn/LexerATNSimulator.java
@@ -261,7 +261,7 @@ public class LexerATNSimulator extends ATNSimulator {
 		return failOrAccept(prevAccept, input, reach, t);
 	}
 
-	protected int execATN(@NotNull CharStream input, @NotNull ATNConfigSet s0, @Nullable DFAState ds0) {
+	protected int execATN(@NotNull CharStream input, @NotNull ATNConfigSet s0, @NotNull DFAState ds0) {
 		//System.out.println("enter exec index "+input.index()+" from "+s0);
 		@NotNull
 		ATNConfigSet closure = s0;
@@ -271,6 +271,7 @@ public class LexerATNSimulator extends ATNSimulator {
 
 		traceLookahead1();
 		int t = input.LA(1);
+		@NotNull
 		DFAState s = ds0; // s is current/from DFA state
 
 		while ( true ) { // while more work
@@ -325,6 +326,7 @@ public class LexerATNSimulator extends ATNSimulator {
 					// we reached state associated with closure for sure, so
 					// make sure it's defined. worst case, we define s0 from
 					// start state configs.
+					@NotNull
 					DFAState from = s != null ? s : addDFAState(closure);
 					// we got nowhere on t, don't throw out this knowledge; it'd
 					// cause a failover from DFA later.
@@ -387,7 +389,7 @@ public class LexerATNSimulator extends ATNSimulator {
 	 *  we can reach upon input {@code t}. Parameter {@code reach} is a return
 	 *  parameter.
 	 */
-	protected void getReachableConfigSet(ATNConfigSet closure, ATNConfigSet reach, int t) {
+	protected void getReachableConfigSet(@NotNull ATNConfigSet closure, @NotNull ATNConfigSet reach, int t) {
 		// this is used to skip processing for configs which have a lower priority
 		// than a config that already reached an accept state for the same rule
 		int skipAlt = ATN.INVALID_ALT_NUMBER;
@@ -417,6 +419,7 @@ public class LexerATNSimulator extends ATNSimulator {
 		}
 	}
 
+	@NotNull
 	protected ATNConfigSet processAcceptConfigs(@NotNull CharStream input, @NotNull ATNConfigSet reach) {
 		if ( debug ) {
 			System.out.format("processAcceptConfigs: reach=%s, prevAccept=%s, prevIndex=%d\n",
@@ -668,6 +671,7 @@ public class LexerATNSimulator extends ATNSimulator {
 		settings.dfaState = null;
 	}
 
+	@NotNull
 	protected DFAState addDFAEdge(@NotNull DFAState from,
 								  int t,
 								  @NotNull ATNConfigSet q)
@@ -681,6 +685,8 @@ public class LexerATNSimulator extends ATNSimulator {
 		 */
 		boolean suppressEdge = q.hasSemanticContext;
 		q.hasSemanticContext = false;
+
+		@NotNull
 		DFAState to = addDFAState(q);
 
 		// even if we can add the states, we can't add an edge for labels out of range
@@ -715,7 +721,7 @@ public class LexerATNSimulator extends ATNSimulator {
 		configuration containing an ATN rule stop state. Later, when
 		traversing the DFA, we will know which rule to accept.
 	 */
-	@Nullable
+	@NotNull
 	protected DFAState addDFAState(@NotNull ATNConfigSet configs) {
 		/* the lexer evaluates predicates on-the-fly; by this point configs
 		 * should not contain any configurations with unevaluated predicates.