rm singleton set; didn't help.

runtime/Java/src/org/antlr/v4/runtime/atn/ATNConfigSet.java

@@ -30,7 +30,6 @@
 package org.antlr.v4.runtime.atn;
 
 import org.antlr.v4.runtime.misc.Array2DHashSet;
-import org.antlr.v4.runtime.misc.EquivalenceSet;
 import org.antlr.v4.runtime.misc.IntervalSet;
 
 import java.util.ArrayList;
@@ -272,7 +271,7 @@ public class ATNConfigSet implements Set<ATNConfig> {
 	/** All configs but hashed by (s, i, _, pi) not incl context.  Wiped out
 	 *  when we go readonly as this set becomes a DFA state.
 	 */
-	public EquivalenceSet<ATNConfig> configLookup;
+	public ConfigHashSet configLookup;
 
 	/** Track the elements as they are added to the set; supports get(i) */
 	public final ArrayList<ATNConfig> configs = new ArrayList<ATNConfig>(7);

runtime/Java/src/org/antlr/v4/runtime/misc/Array2DHashSet.java

@@ -32,7 +32,6 @@ public class Array2DHashSet<T> implements EquivalenceSet<T> {
 	/** Add o to set if not there; return existing value if already there.
 	 *  Absorb is used as synonym for add.
 	 */
-	@Override
 	public T absorb(T o) {
 		if ( n > threshold ) expand();
 		return absorb_(o);

runtime/Java/src/org/antlr/v4/runtime/misc/EquivalenceSet.java

@@ -1,10 +1,12 @@
 package org.antlr.v4.runtime.misc;
 
+import java.util.Set;
+
 /** A set that allows us to override equivalence.  For a single set, we might
  *  want multiple subset perspectives as defined by different hash code
  *  and equivalence methods. HashSet does not allow us to subclass and
  *  override the equivalence operations, so we have to implement our own
  *  sets that are flexible in terms of equivalence.
  */
-public interface EquivalenceSet<T> extends ExtSet<T>, EquivalenceRelation<T> {
+public interface EquivalenceSet<T> extends Set<T>, EquivalenceRelation<T> {
 }

runtime/Java/src/org/antlr/v4/runtime/misc/ExtSet.java

@@ -1,10 +0,0 @@
-package org.antlr.v4.runtime.misc;
-
-import java.util.Set;
-
-public interface ExtSet<T> extends Set<T> {
-	/** Add o to set if not there; return existing value if already there.
-	 *  Absorb is used as synonym for add.  Need to "fix" Set to be smarter.
-	 */
-	public T absorb(T o);
-}

runtime/Java/src/org/antlr/v4/runtime/misc/SingletonSet.java

@@ -1,121 +0,0 @@
-package org.antlr.v4.runtime.misc;
-
-import java.util.Collection;
-import java.util.Iterator;
-import java.util.NoSuchElementException;
-
-/** A set with a single element. */
-public class SingletonSet<T> implements EquivalenceSet<T> {
-	protected T element = null;
-
-	public SingletonSet(T o) {
-		element = o;
-	}
-
-	@Override
-	public T absorb(T o) {
-		if ( o==null ) {
-			element = o;
-			return o;
-		}
-		if ( element.equals(o) ) return element;
-		throw new IllegalStateException("Can't add more than one to a singleton set");
-	}
-
-	@Override
-	public int hashCode(T o) {
-		return o!=null ? o.hashCode() : 0;
-	}
-
-	@Override
-	public boolean equals(T a, T b) {
-		return a==b || a.equals(b);
-	}
-
-	@Override
-	public boolean add(T o) {
-		T a = absorb(o);
-		return a!=o;
-	}
-
-	@Override
-	public int size() {
-		return element!=null ? 1 : 0;
-	}
-
-	@Override
-	public boolean isEmpty() {
-		return element==null;
-	}
-
-	@Override
-	public boolean contains(Object o) {
-		return element!=null &&
-			   (o==element || element.equals(o));
-	}
-
-	@Override
-	public Iterator<T> iterator() {
-		return new Iterator<T>() {
-			boolean returned = false;
-			@Override
-			public boolean hasNext() { return !returned; }
-
-			@Override
-			public T next() {
-				if ( hasNext() ) return element;
-				throw new NoSuchElementException();
-			}
-
-			@Override
-			public void remove() { element = null; }
-		};
-	}
-
-	@Override
-	public Object[] toArray() {
-		Object[] a = { element };
-		if ( !isEmpty() ) return a;
-		return new Object[0];
-	}
-
-	@Override
-	public <U> U[] toArray(U[] a) {
-		if ( !isEmpty() ) { a[0] = (U)element; return a; }
-		return a;
-	}
-
-	@Override
-	public boolean remove(Object o) {
-		if ( isEmpty() ) return false;
-		if ( element.equals(o) ) { element = null; return true; }
-		return false;
-	}
-
-	@Override
-	public boolean containsAll(Collection<?> c) {
-		return size() == c.size() && this.contains(c.toArray()[0]);
-	}
-
-	@Override
-	public boolean addAll(Collection<? extends T> c) {
-		boolean changed = false;
-		for (T o : c) {
-			changed |= add(o);
-		}
-		return changed;
-	}
-
-	@Override
-	public boolean retainAll(Collection<?> c) {
-		throw new UnsupportedOperationException();
-	}
-
-	@Override
-	public boolean removeAll(Collection<?> c) {
-		return false;
-	}
-
-	@Override
-	public void clear() { element = null; }
-}