diff --git a/runtime/Java/src/org/antlr/v4/runtime/RuleContext.java b/runtime/Java/src/org/antlr/v4/runtime/RuleContext.java
index 904bec5b3..3a4f26d2a 100644
--- a/runtime/Java/src/org/antlr/v4/runtime/RuleContext.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/RuleContext.java
@@ -298,7 +298,7 @@ public class RuleContext implements ParseTree.RuleNode {
 	public int getRuleIndex() { return -1; }
 
 	public Interval getSourceInterval() {
-		if ( getChildCount()==0 ) return Interval.ZeroLength;
+		if ( getChildCount()==0 ) return Interval.INVALID;
 		int start = getChild(0).getSourceInterval().a;
 		int stop = getChild(getChildCount()-1).getSourceInterval().b;
 		return new Interval(start, stop);
diff --git a/runtime/Java/src/org/antlr/v4/runtime/misc/Interval.java b/runtime/Java/src/org/antlr/v4/runtime/misc/Interval.java
index e1113c583..30c7e8d31 100644
--- a/runtime/Java/src/org/antlr/v4/runtime/misc/Interval.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/misc/Interval.java
@@ -1,30 +1,30 @@
 /*
  [The "BSD license"]
- Copyright (c) 2011 Terence Parr
- All rights reserved.
+  Copyright (c) 2011 Terence Parr
+  All rights reserved.
 
- Redistribution and use in source and binary forms, with or without
- modification, are permitted provided that the following conditions
- are met:
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions
+  are met:
 
- 1. Redistributions of source code must retain the above copyright
-    notice, this list of conditions and the following disclaimer.
- 2. Redistributions in binary form must reproduce the above copyright
-    notice, this list of conditions and the following disclaimer in the
-    documentation and/or other materials provided with the distribution.
- 3. The name of the author may not be used to endorse or promote products
-    derived from this software without specific prior written permission.
+  1. Redistributions of source code must retain the above copyright
+     notice, this list of conditions and the following disclaimer.
+  2. Redistributions in binary form must reproduce the above copyright
+     notice, this list of conditions and the following disclaimer in the
+     documentation and/or other materials provided with the distribution.
+  3. The name of the author may not be used to endorse or promote products
+     derived from this software without specific prior written permission.
 
- THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
- IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
- OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
- IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
- INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
- NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
- THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 package org.antlr.v4.runtime.misc;
 
@@ -32,7 +32,7 @@ package org.antlr.v4.runtime.misc;
 public class Interval {
 	public static final int INTERVAL_POOL_MAX_VALUE = 1000;
 
-	public static final Interval ZeroLength = new Interval(0,-1);
+	public static final Interval INVALID = new Interval(-1,-2);
 
 	static Interval[] cache = new Interval[INTERVAL_POOL_MAX_VALUE+1];
 
diff --git a/runtime/Java/src/org/antlr/v4/runtime/tree/ParseTree.java b/runtime/Java/src/org/antlr/v4/runtime/tree/ParseTree.java
index 1afcfc200..6d8248ff3 100644
--- a/runtime/Java/src/org/antlr/v4/runtime/tree/ParseTree.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/tree/ParseTree.java
@@ -1,35 +1,36 @@
 /*
  [The "BSD license"]
- Copyright (c) 2011 Terence Parr
- All rights reserved.
+  Copyright (c) 2011 Terence Parr
+  All rights reserved.
 
- Redistribution and use in source and binary forms, with or without
- modification, are permitted provided that the following conditions
- are met:
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions
+  are met:
 
- 1. Redistributions of source code must retain the above copyright
-    notice, this list of conditions and the following disclaimer.
- 2. Redistributions in binary form must reproduce the above copyright
-    notice, this list of conditions and the following disclaimer in the
-    documentation and/or other materials provided with the distribution.
- 3. The name of the author may not be used to endorse or promote products
-    derived from this software without specific prior written permission.
+  1. Redistributions of source code must retain the above copyright
+     notice, this list of conditions and the following disclaimer.
+  2. Redistributions in binary form must reproduce the above copyright
+     notice, this list of conditions and the following disclaimer in the
+     documentation and/or other materials provided with the distribution.
+  3. The name of the author may not be used to endorse or promote products
+     derived from this software without specific prior written permission.
 
- THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
- IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
- OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
- IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
- INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
- NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
- THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 package org.antlr.v4.runtime.tree;
 
-import org.antlr.v4.runtime.*;
+import org.antlr.v4.runtime.RuleContext;
+import org.antlr.v4.runtime.Token;
 import org.antlr.v4.runtime.misc.Interval;
 
 /** An interface to access the tree of RuleContext objects created
@@ -65,7 +66,7 @@ public interface ParseTree extends SyntaxTree {
 		public Token getPayload() { return token; }
 
 		public Interval getSourceInterval() {
-			if ( token==null ) return Interval.ZeroLength;
+			if ( token==null ) return Interval.INVALID;
 			return new Interval(token.getTokenIndex(), token.getTokenIndex());
 		}