fix #1177 (LB(k) stops at index 0) @antlr/antlr-targets might care ab…

…out this
antlr · Dec 10, 2016 · 0a7e90f · 0a7e90f
1 parent 9ef7560
commit 0a7e90f
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/runtime/Java/src/org/antlr/v4/runtime/CommonTokenStream.java b/runtime/Java/src/org/antlr/v4/runtime/CommonTokenStream.java
@@ -77,7 +77,7 @@ protected Token LB(int k) {
         int i = p;
         int n = 1;
         // find k good tokens looking backwards
-        while ( n<=k ) {
+        while ( n<=k && i>0 ) {
             // skip off-channel tokens
             i = previousTokenOnChannel(i - 1, channel);
             n++;