add simple LL(2) rule with ATN debug output.

Signed-off-by: Terence Parr <parrt@antlr.org>

runtime-testsuite/resources/org/antlr/v4/test/runtime/descriptors/TraceParserATN/LL2Trace.txt

@@ -0,0 +1,52 @@
+[type]
+Parser
+
+[grammar]
+grammar T;
+s : t EOF ;
+t : ID ';' | ID '.' ;
+ID  : [a-zA-Z]+ ;
+WS  : [ \r\n\t]+ -> skip ;
+
+[start]
+s
+
+[input]
+xyz.
+
+[output]
+"""adaptivePredict decision 0 exec LA(1)==ID<3> line 1:0
+predictATN decision 0 exec LA(1)==ID<3>, outerContext=[t s]
+closure((7,1,[$]))
+closure((9,2,[$]))
+adding new DFA state: 0:[(7,1,[$]), (9,2,[$])]
+execATN decision 0 exec LA(1)==ID<3> line 1:0
+s0 = 0:[(7,1,[$]), (9,2,[$])]
+in computeReachSet, starting closure: [(7,1,[$]), (9,2,[$])]
+testing ID<3> at (7,1,[$])
+testing ID<3> at (9,2,[$])
+closure((8,1,[$]))
+closure((10,2,[$]))
+SLL altSubSets=[{1}, {2}], configs=[(8,1,[$]), (10,2,[$])], predict=0, allSubsetsConflict=false, conflictingAlts={1, 2}
+EDGE 0:[(7,1,[$]), (9,2,[$])] -> -1:[(8,1,[$]), (10,2,[$])] upon ID<3>
+adding new DFA state: 1:[(8,1,[$]), (10,2,[$])]
+DFA=
+s0-ID->s1
+
+in computeReachSet, starting closure: [(8,1,[$]), (10,2,[$])]
+testing '.'<2> at (8,1,[$])
+testing '.'<2> at (10,2,[$])
+SLL altSubSets=[{2}], configs=[(12,2,[$])], predict=2, allSubsetsConflict=false, conflictingAlts={2}
+EDGE 1:[(8,1,[$]), (10,2,[$])] -> -1:[(12,2,[$])],uniqueAlt=2=>2 upon '.'<2>
+adding new DFA state: 2:[(12,2,[$])],uniqueAlt=2=>2
+DFA=
+s0-ID->s1
+s1-'.'->:s2=>2
+
+DFA after predictATN: s0-ID->s1
+s1-'.'->:s2=>2
+
+"""
+
+[flags]
+traceATN

runtime-testsuite/test/org/antlr/v4/test/runtime/java/JavaRunner.java

@@ -185,14 +185,21 @@ private ExecutedState execCommon(JavaCompiledState compiledState) {
 			stdoutReader.start();
 			stderrReader.start();
 
+			PrintStream saveStdout = System.out;
+			ByteArrayOutputStream captureNormalStdout = new ByteArrayOutputStream();
+			System.setOut(new PrintStream(captureNormalStdout));
+
 			recognizeMethod.invoke(null, new File(getTempDirPath(), "input").getAbsolutePath(),
 					new PrintStream(stdoutOut), new PrintStream(stderrOut));
 
+			System.setOut(saveStdout);
+
 			stdoutOut.close();
 			stderrOut.close();
 			stdoutReader.join();
 			stderrReader.join();
-			output = stdoutReader.toString();
+			// include normal stdout to get print statements from ATN simulation debugging
+			output = stdoutReader.toString() + captureNormalStdout;
 			errors = stderrReader.toString();
 		} catch (Exception ex) {
 			exception = ex;