diff --git a/com.ibm.wala.core/src/com/ibm/wala/cfg/AbstractCFG.java b/com.ibm.wala.core/src/com/ibm/wala/cfg/AbstractCFG.java
index edf5ec8da..9d50b6e64 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/cfg/AbstractCFG.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/cfg/AbstractCFG.java
@@ -634,7 +634,7 @@ public abstract class AbstractCFG implements ControlFlowGraph, Constants {
     return Iterator2Collection.toCollection(iterateNormalPredecessors(b));
   }
 
-  public IntSet getPredNodeNumbers(IBasicBlock node) {
+  public IntSet getPredNodeNumbers(IBasicBlock node) throws UnimplementedError {
     Assertions.UNREACHABLE();
     return null;
   }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/cfg/TwoExitCFG.java b/com.ibm.wala.core/src/com/ibm/wala/cfg/TwoExitCFG.java
index beb301876..546bec775 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/cfg/TwoExitCFG.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/cfg/TwoExitCFG.java
@@ -543,11 +543,11 @@ public class TwoExitCFG implements ControlFlowGraph {
     return new NumberedNodeIterator<IBasicBlock>(s, this);
   }
 
-  public void removeIncomingEdges(IBasicBlock node) {
+  public void removeIncomingEdges(IBasicBlock node) throws UnsupportedOperationException {
     throw new UnsupportedOperationException();
   }
 
-  public void removeOutgoingEdges(IBasicBlock node) {
+  public void removeOutgoingEdges(IBasicBlock node) throws UnsupportedOperationException {
     throw new UnsupportedOperationException();
   }
 
diff --git a/com.ibm.wala.core/src/com/ibm/wala/classLoader/SyntheticMethod.java b/com.ibm.wala.core/src/com/ibm/wala/classLoader/SyntheticMethod.java
index 9dacbca16..39671fcfb 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/classLoader/SyntheticMethod.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/classLoader/SyntheticMethod.java
@@ -152,7 +152,7 @@ public class SyntheticMethod implements IMethod {
     return new InducedCFG(getStatements(), this, Everywhere.EVERYWHERE);
   }
 
-  public BytecodeStream getBytecodeStream()  {
+  public BytecodeStream getBytecodeStream() throws UnsupportedOperationException  {
     throw new UnsupportedOperationException();
   }
 
diff --git a/com.ibm.wala.core/src/com/ibm/wala/dataflow/IFDS/ExplodedSupergraph.java b/com.ibm.wala.core/src/com/ibm/wala/dataflow/IFDS/ExplodedSupergraph.java
index 3fcd88970..583289f49 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/dataflow/IFDS/ExplodedSupergraph.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/dataflow/IFDS/ExplodedSupergraph.java
@@ -217,7 +217,7 @@ public class ExplodedSupergraph<T> implements Graph<ExplodedSupergraphNode<T>> {
     return count;
   }
 
-  public void addEdge(ExplodedSupergraphNode src, ExplodedSupergraphNode dst) {
+  public void addEdge(ExplodedSupergraphNode src, ExplodedSupergraphNode dst) throws UnsupportedOperationException {
     throw new UnsupportedOperationException();
   }
   
diff --git a/com.ibm.wala.core/src/com/ibm/wala/dataflow/IFDS/PartiallyCollapsedSupergraph.java b/com.ibm.wala.core/src/com/ibm/wala/dataflow/IFDS/PartiallyCollapsedSupergraph.java
index 4f4b69b1b..1c383c460 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/dataflow/IFDS/PartiallyCollapsedSupergraph.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/dataflow/IFDS/PartiallyCollapsedSupergraph.java
@@ -264,8 +264,8 @@ public class PartiallyCollapsedSupergraph extends AbstractGraph<Object> implemen
       throw new IllegalArgumentException(
           "(n instanceof com.ibm.wala.cfg.IBasicBlock) and (not ( n instanceof com.ibm.wala.ipa.cfg.BasicBlockInContext ) )");
     }
-    if (n instanceof IBasicBlock) {
-      return partialIPFG.getCGNode((IBasicBlock) n);
+    if (n instanceof BasicBlockInContext) {
+      return partialIPFG.getCGNode((BasicBlockInContext) n);
     } else {
       return nodeManager.getProcOfCollapsedNode(n);
     }
@@ -294,9 +294,8 @@ public class PartiallyCollapsedSupergraph extends AbstractGraph<Object> implemen
      */
     private void computeTransverseEdges() {
       // compute transverse edges that originate from basic blocks
-      for (Iterator it = partialIPFG.iterator(); it.hasNext();) {
-        IBasicBlock bb = (IBasicBlock) it.next();
-        if (partialIPFG.hasCall((BasicBlockInContext) bb)) {
+      for (BasicBlockInContext bb:  partialIPFG) {
+        if (partialIPFG.hasCall(bb)) {
           Set targets = partialIPFG.getCallTargets(bb);
           for (Iterator it2 = targets.iterator(); it2.hasNext();) {
             CGNode n = (CGNode) it2.next();
@@ -851,8 +850,8 @@ public class PartiallyCollapsedSupergraph extends AbstractGraph<Object> implemen
    * @see com.ibm.wala.dataflow.IFDS.ISupergraph#isReturn(java.lang.Object)
    */
   public boolean isReturn(Object object) {
-    if (object instanceof IBasicBlock) {
-      return partialIPFG.isReturn(object);
+    if (object instanceof BasicBlockInContext) {
+      return partialIPFG.isReturn((BasicBlockInContext)object);
     } else {
       if (nodeManager.isCollapsedExit(object)) {
         CGNode node = getProcOf(object);
diff --git a/com.ibm.wala.core/src/com/ibm/wala/demandpa/alg/SimpleDemandPointsTo.java b/com.ibm.wala.core/src/com/ibm/wala/demandpa/alg/SimpleDemandPointsTo.java
index b04a198b9..1a2418525 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/demandpa/alg/SimpleDemandPointsTo.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/demandpa/alg/SimpleDemandPointsTo.java
@@ -56,6 +56,7 @@ import com.ibm.wala.util.collections.FilterIterator;
 import com.ibm.wala.util.collections.Iterator2Collection;
 import com.ibm.wala.util.debug.Assertions;
 import com.ibm.wala.util.debug.Trace;
+import com.ibm.wala.util.debug.UnimplementedError;
 import com.ibm.wala.util.graph.traverse.SlowDFSDiscoverTimeIterator;
 
 /**
@@ -74,7 +75,7 @@ public class SimpleDemandPointsTo extends AbstractDemandPointsTo {
   }
 
   @SuppressWarnings("unchecked")
-  public Collection<InstanceKey> getPointsTo(PointerKey pk) {
+  public Collection<InstanceKey> getPointsTo(PointerKey pk) throws UnimplementedError {
 
     Assertions._assert(pk instanceof LocalPointerKey, "we only handle locals");
     LocalPointerKey lpk = (LocalPointerKey) pk;
diff --git a/com.ibm.wala.core/src/com/ibm/wala/fixedpoint/impl/UnaryStatement.java b/com.ibm.wala.core/src/com/ibm/wala/fixedpoint/impl/UnaryStatement.java
index 675a6b039..7d8e612eb 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/fixedpoint/impl/UnaryStatement.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/fixedpoint/impl/UnaryStatement.java
@@ -158,7 +158,7 @@ public abstract class UnaryStatement extends AbstractStatement {
     return result;
   }
   
-  public IVariable[] getRHS() {
+  public IVariable[] getRHS() throws UnsupportedOperationException {
     // This should never be called ...use the more efficient getRightHandSide instead
     throw new UnsupportedOperationException();
   }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/OneCFABuilder.java b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/OneCFABuilder.java
index 109658f71..142e20dc6 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/OneCFABuilder.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/OneCFABuilder.java
@@ -31,7 +31,10 @@ import com.ibm.wala.ipa.cha.IClassHierarchy;
 public class OneCFABuilder extends CFABuilder {
 
   public static OneCFABuilder make(IClassHierarchy cha, AnalysisOptions options, AnalysisCache cache,
-      ContextSelector appContextSelector, SSAContextInterpreter appContextInterpreter, ReflectionSpecification reflect) {
+      ContextSelector appContextSelector, SSAContextInterpreter appContextInterpreter, ReflectionSpecification reflect) throws IllegalArgumentException {
+    if (options == null) {
+          throw new IllegalArgumentException("options == null");
+        }
     return new OneCFABuilder(cha, options, cache, appContextSelector, appContextInterpreter, reflect);
   }
 
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/ZeroXCFABuilder.java b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/ZeroXCFABuilder.java
index c4bb93b35..a24e027df 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/ZeroXCFABuilder.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/ZeroXCFABuilder.java
@@ -99,7 +99,10 @@ public class ZeroXCFABuilder extends CFABuilder {
 
   public static ZeroXCFABuilder make(IClassHierarchy cha, AnalysisOptions options, AnalysisCache cache,
       ContextSelector appContextSelector, SSAContextInterpreter appContextInterpreter, ReflectionSpecification reflect,
-      int instancePolicy) {
+      int instancePolicy) throws IllegalArgumentException {
+    if (options == null) {
+      throw new IllegalArgumentException("options == null");
+    }
     return new ZeroXCFABuilder(cha, options, cache, appContextSelector, appContextInterpreter, reflect, instancePolicy);
   }
 
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ipa/cfg/InterproceduralCFG.java b/com.ibm.wala.core/src/com/ibm/wala/ipa/cfg/InterproceduralCFG.java
index a22e3120c..0da54bab4 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ipa/cfg/InterproceduralCFG.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ipa/cfg/InterproceduralCFG.java
@@ -526,32 +526,32 @@ public class InterproceduralCFG implements NumberedGraph<BasicBlockInContext> {
       }
       BasicBlockInContext b = new BasicBlockInContext(N, bb);
       G.addNode(b);
-      if (hasCall(bb, cfg)) {
+      if (hasCall(b, cfg)) {
         hasCallVector.set(getNumber(b));
       }
     }
   }
 
   /**
-   * @param B
    * @return the original CFG from whence B came
+   * @throws IllegalArgumentException  if B == null
    */
-  public ControlFlowGraph getCFG(IBasicBlock B) {
-    if (Assertions.verifyAssertions) {
-      Assertions._assert(B instanceof BasicBlockInContext);
+  public ControlFlowGraph getCFG(BasicBlockInContext B) throws IllegalArgumentException {
+    if (B == null) {
+      throw new IllegalArgumentException("B == null");
     }
     return getCFG(getCGNode(B));
   }
 
   /**
-   * @param B
    * @return the original CGNode from whence B came
+   * @throws IllegalArgumentException  if B == null
    */
-  public CGNode getCGNode(IBasicBlock B) {
-    if (Assertions.verifyAssertions) {
-      Assertions._assert(B instanceof BasicBlockInContext);
+  public CGNode getCGNode(BasicBlockInContext B) throws IllegalArgumentException {
+    if (B == null) {
+      throw new IllegalArgumentException("B == null");
     }
-    return ((BasicBlockInContext) B).getNode();
+    return B.getNode();
   }
 
   /*
@@ -662,10 +662,9 @@ public class InterproceduralCFG implements NumberedGraph<BasicBlockInContext> {
   }
 
   /**
-   * @param B
    * @return true iff basic block B ends in a call instuction
    */
-  private boolean hasCall(IBasicBlock B, ControlFlowGraph cfg) {
+  private boolean hasCall(BasicBlockInContext B, ControlFlowGraph cfg) {
     IInstruction[] statements = cfg.getInstructions();
 
     int lastIndex = B.getLastInstructionIndex();
@@ -692,13 +691,10 @@ public class InterproceduralCFG implements NumberedGraph<BasicBlockInContext> {
    * @throws IllegalArgumentException
    *             if B is null
    */
-  public Set<CGNode> getCallTargets(IBasicBlock B) {
+  public Set<CGNode> getCallTargets(BasicBlockInContext B) {
     if (B == null) {
       throw new IllegalArgumentException("B is null");
     }
-    if (Assertions.verifyAssertions) {
-      Assertions._assert(B instanceof BasicBlockInContext);
-    }
     ControlFlowGraph cfg = getCFG(B);
     return getCallTargets(B, cfg, getCGNode(B));
   }
@@ -814,11 +810,10 @@ public class InterproceduralCFG implements NumberedGraph<BasicBlockInContext> {
     }
   };
 
-  public boolean isReturn(Object object) {
-    if (Assertions.verifyAssertions) {
-      Assertions._assert(object instanceof BasicBlockInContext);
+  public boolean isReturn(BasicBlockInContext bb) throws IllegalArgumentException {
+    if (bb == null) {
+      throw new IllegalArgumentException("bb == null");
     }
-    BasicBlockInContext bb = (BasicBlockInContext) object;
     ControlFlowGraph cfg = getCFG(bb);
     for (Iterator it = cfg.getPredNodes(bb.getDelegate()); it.hasNext();) {
       IBasicBlock b = (IBasicBlock) it.next();
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ipa/slicer/HeapReachingDefs.java b/com.ibm.wala.core/src/com/ibm/wala/ipa/slicer/HeapReachingDefs.java
index 0fdf2a2aa..ea1a9915d 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ipa/slicer/HeapReachingDefs.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ipa/slicer/HeapReachingDefs.java
@@ -207,6 +207,7 @@ public class HeapReachingDefs {
       return result;
     }
 
+    @Override
     public String toString() {
       return delegate.toString();
     }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ssa/SSABuilder.java b/com.ibm.wala.core/src/com/ibm/wala/ssa/SSABuilder.java
index 0eba2eb66..1411588c2 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ssa/SSABuilder.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ssa/SSABuilder.java
@@ -58,7 +58,10 @@ import com.ibm.wala.util.intset.IntPair;
 public class SSABuilder extends AbstractIntStackMachine {
 
   public static SSABuilder make(ShrikeCTMethod method, SSACFG cfg, ShrikeCFG scfg, SSAInstruction[] instructions,
-      SymbolTable symbolTable, boolean buildLocalMap, boolean addPiNodes) {
+      SymbolTable symbolTable, boolean buildLocalMap, boolean addPiNodes) throws IllegalArgumentException {
+    if (scfg == null) {
+      throw new IllegalArgumentException("scfg == null");
+    }
     return new SSABuilder(method, cfg, scfg, instructions, symbolTable, buildLocalMap, addPiNodes);
   }
 
@@ -78,8 +81,8 @@ public class SSABuilder extends AbstractIntStackMachine {
    */
   private final SSA2LocalMap localMap;
 
-  private SSABuilder(ShrikeCTMethod method, SSACFG cfg, ShrikeCFG scfg, SSAInstruction[] instructions,
-      SymbolTable symbolTable, boolean buildLocalMap, boolean addPiNodes) {
+  private SSABuilder(ShrikeCTMethod method, SSACFG cfg, ShrikeCFG scfg, SSAInstruction[] instructions, SymbolTable symbolTable,
+      boolean buildLocalMap, boolean addPiNodes) {
     super(scfg);
     localMap = buildLocalMap ? new SSA2LocalMap(scfg, instructions.length, cfg.getNumberOfNodes(), maxLocals) : null;
     init(new SymbolTableMeeter(symbolTable, cfg, instructions, scfg), new SymbolicPropagator(scfg, instructions, symbolTable,
@@ -604,10 +607,10 @@ public class SSABuilder extends AbstractIntStackMachine {
         NewSiteReference ref = NewSiteReference.make(getCurrentProgramCounter(), t);
         if (t.isArrayType()) {
           int[] sizes = new int[t.getDimensionality()];
-          for (int i = 0; i<instruction.getArrayBoundsCount(); i++) {
+          for (int i = 0; i < instruction.getArrayBoundsCount(); i++) {
             sizes[i] = workingState.pop();
           }
-          for (int i = instruction.getArrayBoundsCount(); i< sizes.length; i++) {
+          for (int i = instruction.getArrayBoundsCount(); i < sizes.length; i++) {
             sizes[i] = symbolTable.getConstant(0);
           }
           emitInstruction(new SSANewInstruction(result, ref, sizes));
@@ -815,9 +818,9 @@ public class SSABuilder extends AbstractIntStackMachine {
 
     /**
      * @param nInstructions
-     *          number of instructions in the bytecode for this method
+     *            number of instructions in the bytecode for this method
      * @param nBlocks
-     *          number of basic blocks in the CFG
+     *            number of basic blocks in the CFG
      */
     SSA2LocalMap(ShrikeCFG shrikeCfg, int nInstructions, int nBlocks, int maxLocals) {
       shrikeCFG = shrikeCfg;
@@ -862,9 +865,9 @@ public class SSABuilder extends AbstractIntStackMachine {
 
     /**
      * @param index -
-     *          index into IR instruction array
+     *            index into IR instruction array
      * @param vn -
-     *          value number
+     *            value number
      */
     public String[] getLocalNames(int index, int vn) {
       try {
@@ -892,9 +895,9 @@ public class SSABuilder extends AbstractIntStackMachine {
 
     /**
      * @param pc
-     *          a program counter (index into ShrikeBT instruction array)
+     *            a program counter (index into ShrikeBT instruction array)
      * @param vn
-     *          a value number
+     *            a value number
      * @return if we know that immediately after the given program counter, v_vn
      *         corresponds to some set of locals, then return an array of the
      *         local numbers. else return null.
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ssa/analysis/ExplodedControlFlowGraph.java b/com.ibm.wala.core/src/com/ibm/wala/ssa/analysis/ExplodedControlFlowGraph.java
index e0355b124..a3c3f4d28 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ssa/analysis/ExplodedControlFlowGraph.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ssa/analysis/ExplodedControlFlowGraph.java
@@ -213,7 +213,7 @@ public class ExplodedControlFlowGraph implements ControlFlowGraph {
     throw new UnsupportedOperationException();
   }
 
-  public void addNode(IBasicBlock n) {
+  public void addNode(IBasicBlock n) throws UnsupportedOperationException {
     throw new UnsupportedOperationException();
   }
 
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/graph/impl/DelegatingNumberedEdgeManager.java b/com.ibm.wala.core/src/com/ibm/wala/util/graph/impl/DelegatingNumberedEdgeManager.java
index d470f48e5..f0520545f 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/graph/impl/DelegatingNumberedEdgeManager.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/graph/impl/DelegatingNumberedEdgeManager.java
@@ -137,7 +137,7 @@ public class DelegatingNumberedEdgeManager<T extends INodeWithNumberedEdges> imp
   /*
    * @see com.ibm.wala.util.graph.EdgeManager#removeEdges(com.ibm.wala.util.graph.Node)
    */
-  public void removeAllIncidentEdges(T node) {
+  public void removeAllIncidentEdges(T node) throws UnimplementedError {
     if (node == null) {
       throw new IllegalArgumentException("node is null");
     }
@@ -148,7 +148,7 @@ public class DelegatingNumberedEdgeManager<T extends INodeWithNumberedEdges> imp
   /*
    * @see com.ibm.wala.util.graph.EdgeManager#removeEdges(com.ibm.wala.util.graph.Node)
    */
-  public void removeIncomingEdges(T node) {
+  public void removeIncomingEdges(T node) throws UnimplementedError {
     if (node == null) {
       throw new IllegalArgumentException("node cannot be null");
     }
@@ -159,7 +159,7 @@ public class DelegatingNumberedEdgeManager<T extends INodeWithNumberedEdges> imp
   /*
    * @see com.ibm.wala.util.graph.EdgeManager#removeEdges(com.ibm.wala.util.graph.Node)
    */
-  public void removeOutgoingEdges(T node) {
+  public void removeOutgoingEdges(T node) throws UnimplementedError {
     if (node == null) {
       throw new IllegalArgumentException("node cannot be null");
     }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/graph/impl/SparseNumberedEdgeManager.java b/com.ibm.wala.core/src/com/ibm/wala/util/graph/impl/SparseNumberedEdgeManager.java
index 9b2f2bb3d..c09b29521 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/graph/impl/SparseNumberedEdgeManager.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/graph/impl/SparseNumberedEdgeManager.java
@@ -52,8 +52,12 @@ public final class SparseNumberedEdgeManager<T> implements NumberedEdgeManager<T
    *          an object to track nodes
    * @param normalCase
    *          what is the "normal" number of out edges for a node?
+   * @throws IllegalArgumentException  if normalCase < 0
    */
-  public SparseNumberedEdgeManager(NumberedNodeManager<T> nodeManager, int normalCase, byte delegateImpl) {
+  public SparseNumberedEdgeManager(NumberedNodeManager<T> nodeManager, int normalCase, byte delegateImpl) throws IllegalArgumentException {
+    if (normalCase < 0) {
+      throw new IllegalArgumentException("normalCase < 0");
+    }
     this.nodeManager = nodeManager;
     if (normalCase == 0) {
       successors = new BasicNaturalRelation(defaultImpl, delegateImpl);
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/intset/BasicNaturalRelation.java b/com.ibm.wala.core/src/com/ibm/wala/util/intset/BasicNaturalRelation.java
index 1fb815b86..2219fb320 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/intset/BasicNaturalRelation.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/intset/BasicNaturalRelation.java
@@ -74,11 +74,16 @@ public final class BasicNaturalRelation implements IBinaryNaturalRelation {
    * implemented with a SimpleIntVector, and the 2nd and 3rd are implemented
    * with TwoLevelIntVector
    * @throws IllegalArgumentException  if implementation is null
+   * @throws IllegalArgumentException  if implementation.length == 0
    */
-  public BasicNaturalRelation(byte[] implementation, byte vectorImpl) {
+  public BasicNaturalRelation(byte[] implementation, byte vectorImpl) throws IllegalArgumentException {
+
     if (implementation == null) {
       throw new IllegalArgumentException("implementation is null");
     }
+    if (implementation.length == 0) {
+      throw new IllegalArgumentException("implementation.length == 0");
+    }
     smallStore = new IntVector[implementation.length];
     for (int i = 0; i < implementation.length; i++) {
       switch (implementation[i]) {
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/intset/BimodalMutableIntSet.java b/com.ibm.wala.core/src/com/ibm/wala/util/intset/BimodalMutableIntSet.java
index 995212d4d..196d22b4b 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/intset/BimodalMutableIntSet.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/intset/BimodalMutableIntSet.java
@@ -220,7 +220,7 @@ public class BimodalMutableIntSet implements MutableIntSet {
     return impl.max();
   }
 
-  public static BimodalMutableIntSet makeCopy(IntSet B) throws IllegalArgumentException {
+  public static BimodalMutableIntSet makeCopy(IntSet B) throws UnimplementedError, IllegalArgumentException {
     if (B == null) {
       throw new IllegalArgumentException("B == null");
     }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/intset/BimodalMutableIntSetFactory.java b/com.ibm.wala.core/src/com/ibm/wala/util/intset/BimodalMutableIntSetFactory.java
index df870e1cb..c2b2cc32d 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/intset/BimodalMutableIntSetFactory.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/intset/BimodalMutableIntSetFactory.java
@@ -10,6 +10,8 @@
  *******************************************************************************/
 package com.ibm.wala.util.intset;
 
+import com.ibm.wala.util.debug.UnimplementedError;
+
 /**
  * 
  * An object that creates some bimodal mutable int sets.
@@ -41,7 +43,7 @@ public class BimodalMutableIntSetFactory implements MutableIntSetFactory {
   /*
    * @see com.ibm.wala.util.intset.MutableIntSetFactory#make(com.ibm.wala.util.intset.IntSet)
    */
-  public MutableIntSet makeCopy(IntSet x) throws IllegalArgumentException {
+  public MutableIntSet makeCopy(IntSet x) throws UnimplementedError, IllegalArgumentException {
     if (x == null) {
       throw new IllegalArgumentException("x == null");
     }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/intset/MutableSparseLongSet.java b/com.ibm.wala.core/src/com/ibm/wala/util/intset/MutableSparseLongSet.java
index 84563c908..77d50858e 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/intset/MutableSparseLongSet.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/intset/MutableSparseLongSet.java
@@ -37,10 +37,12 @@ public final class MutableSparseLongSet extends SparseLongSet implements Mutable
    */
   private final static int INITIAL_NONEMPTY_SIZE = 2;
 
-  /**
-   * @param set
-   */
-  public MutableSparseLongSet(LongSet set) {
+
+  public static MutableSparseLongSet make(LongSet set) {
+    return new MutableSparseLongSet(set);
+  }
+
+  private MutableSparseLongSet(LongSet set) {
     super();
     copySet(set);
   }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/intset/SparseLongSet.java b/com.ibm.wala.core/src/com/ibm/wala/util/intset/SparseLongSet.java
index 6b222ab88..6e45999cd 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/intset/SparseLongSet.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/intset/SparseLongSet.java
@@ -356,7 +356,7 @@ public class SparseLongSet implements LongSet {
       throw new IllegalArgumentException("that == null");
     }
     if (that instanceof SparseLongSet) {
-      MutableSparseLongSet temp = new MutableSparseLongSet(this);
+      MutableSparseLongSet temp = MutableSparseLongSet.make(this);
       temp.intersectWith((SparseLongSet) that);
       return temp;
     } else {