diff --git a/com.ibm.wala.core/src/com/ibm/wala/analysis/reflection/ReflectionContextSelector.java b/com.ibm.wala.core/src/com/ibm/wala/analysis/reflection/ReflectionContextSelector.java
index 756f0ad77..f845055b0 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/analysis/reflection/ReflectionContextSelector.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/analysis/reflection/ReflectionContextSelector.java
@@ -27,9 +27,13 @@ import com.ibm.wala.ipa.callgraph.propagation.InstanceKey;
 public class ReflectionContextSelector {
 
   public static ContextSelector createReflectionContextSelector(AnalysisOptions options) {
+  
+    if (options == null) {
+      throw new IllegalArgumentException("null options");
+    }
+    
     // start with a dummy
     ContextSelector result = new ContextSelector() {
-
       public Context getCalleeTarget(CGNode caller, CallSiteReference site, IMethod callee, InstanceKey receiver) {
         return null;
       }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/analysis/typeInference/SetType.java b/com.ibm.wala.core/src/com/ibm/wala/analysis/typeInference/SetType.java
index 323de75f8..98daea38c 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/analysis/typeInference/SetType.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/analysis/typeInference/SetType.java
@@ -19,12 +19,8 @@ import com.ibm.wala.util.debug.Assertions;
 import com.ibm.wala.util.debug.UnimplementedError;
 
 /**
- * 
  * Abstraction of a set of PointTypes. These are immutable. TODO: fix for
  * efficiency if needed.
- * 
- * @author sfink
- * 
  */
 public class SetType extends TypeAbstraction {
 
@@ -42,6 +38,9 @@ public class SetType extends TypeAbstraction {
     types = HashSetFactory.make(points.length);
     int h = 0;
     for (int i = 0; i < points.length; i++) {
+      if (points[i] == null) {
+        throw new IllegalArgumentException("points[" + i + "] is null");
+      }
       TypeReference T = points[i].getType().getReference();
       h ^= T.hashCode();
       types.add(T);
diff --git a/com.ibm.wala.core/src/com/ibm/wala/dataflow/graph/BitVectorUnionConstant.java b/com.ibm.wala.core/src/com/ibm/wala/dataflow/graph/BitVectorUnionConstant.java
index ed6712bcd..fbe9c8da4 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/dataflow/graph/BitVectorUnionConstant.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/dataflow/graph/BitVectorUnionConstant.java
@@ -12,7 +12,6 @@ package com.ibm.wala.dataflow.graph;
 
 import com.ibm.wala.fixedpoint.impl.UnaryOperator;
 import com.ibm.wala.fixpoint.BitVectorVariable;
-import com.ibm.wala.util.debug.Assertions;
 
 
 /**
@@ -22,8 +21,8 @@ public class BitVectorUnionConstant extends UnaryOperator<BitVectorVariable> {
   
   private final int c;
   public BitVectorUnionConstant(int c) {
-    if (Assertions.verifyAssertions) {
-      Assertions._assert(c >= 0);
+    if (c < 0) {
+      throw new IllegalArgumentException("Invalid c: " + c);
     }
     this.c = c;
   }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/demandpa/alg/ThisFilteringHeapModel.java b/com.ibm.wala.core/src/com/ibm/wala/demandpa/alg/ThisFilteringHeapModel.java
index d55277bc7..c3b71f089 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/demandpa/alg/ThisFilteringHeapModel.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/demandpa/alg/ThisFilteringHeapModel.java
@@ -124,6 +124,9 @@ import com.ibm.wala.util.debug.Assertions;
     }
 
     public ThisFilteringHeapModel(HeapModel delegate, IClassHierarchy cha) {
+      if (delegate == null) {
+        throw new IllegalArgumentException("delegate null");
+      }
       this.delegate = delegate;
       this.cha = cha;
     }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/escape/TrivialMethodEscape.java b/com.ibm.wala.core/src/com/ibm/wala/escape/TrivialMethodEscape.java
index a065a6b50..707c91f14 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/escape/TrivialMethodEscape.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/escape/TrivialMethodEscape.java
@@ -58,6 +58,9 @@ public class TrivialMethodEscape implements IMethodEscapeAnalysis, INodeEscapeAn
 
   public boolean mayEscape(MethodReference allocMethod, int allocPC, MethodReference m) throws WalaException {
 
+    if (allocMethod == null) {
+      throw new IllegalArgumentException("null allocMethod");
+    }
     // nodes:= set of call graph nodes representing method m
     Set nodes = cg.getNodes(m);
     if (nodes.size() == 0) {
diff --git a/com.ibm.wala.core/src/com/ibm/wala/fixedpoint/impl/GeneralStatement.java b/com.ibm.wala.core/src/com/ibm/wala/fixedpoint/impl/GeneralStatement.java
index 03793e9f4..c08f980e6 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/fixedpoint/impl/GeneralStatement.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/fixedpoint/impl/GeneralStatement.java
@@ -71,6 +71,9 @@ public class GeneralStatement<T extends IVariable> extends AbstractStatement<T,
    */
   public GeneralStatement(T lhs, AbstractOperator<T> operator) {
     super();
+    if (operator == null) {
+      throw new IllegalArgumentException("null operator");
+    }
     this.operator = operator;
     this.lhs = lhs;
     this.rhs = null;
diff --git a/com.ibm.wala.core/src/com/ibm/wala/fixpoint/BitVectorVariable.java b/com.ibm.wala.core/src/com/ibm/wala/fixpoint/BitVectorVariable.java
index 876b19a64..91c9b0819 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/fixpoint/BitVectorVariable.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/fixpoint/BitVectorVariable.java
@@ -66,6 +66,9 @@ public class BitVectorVariable extends AbstractVariable<BitVectorVariable> {
   }
 
   public boolean sameValue(BitVectorVariable other) {
+    if (other == null) {
+      throw new IllegalArgumentException("null other");
+    }
     if (V == null) {
       return (other.V == null);
     } else {
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/impl/Util.java b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/impl/Util.java
index bc87de3be..b333d75f2 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/impl/Util.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/impl/Util.java
@@ -52,8 +52,6 @@ import com.ibm.wala.util.graph.traverse.SlowDFSDiscoverTimeIterator;
 import com.ibm.wala.util.strings.Atom;
 
 /**
- * @author sfink
- * 
  */
 public class Util {
   /**
@@ -498,7 +496,13 @@ public class Util {
     };
   }
 
+  /**
+   * create a set holding the contents of an {@link Iterator}
+   */
   public static <T> Set<T> setify(Iterator<? extends T> x) {
+    if (x == null) {
+      throw new IllegalArgumentException("Null x");
+    }
     Set<T> y = HashSetFactory.make();
     while (x.hasNext()) {
       y.add(x.next());
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/LocalPointerKey.java b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/LocalPointerKey.java
index 5ddbeff82..6257b286d 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/LocalPointerKey.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/LocalPointerKey.java
@@ -28,6 +28,9 @@ public class LocalPointerKey extends AbstractLocalPointerKey {
     if (valueNumber <= 0) {
       throw new IllegalArgumentException("illegal valueNumber: " + valueNumber);
     }
+    if (node == null) {
+      throw new IllegalArgumentException("null node");
+    }
   }
 
   @Override
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/PointerAnalysisImpl.java b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/PointerAnalysisImpl.java
index bf8c47213..a179d9300 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/PointerAnalysisImpl.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/PointerAnalysisImpl.java
@@ -82,10 +82,9 @@ public class PointerAnalysisImpl extends AbstractPointerAnalysis {
     this.pointerKeys = pointerKeys;
     this.iKeyFactory = iKeyFactory;
     this.pointsToMap = pointsToMap;
-    if (Assertions.verifyAssertions) {
-      Assertions._assert(iKeyFactory != null);
+    if (iKeyFactory == null) {
+      throw new IllegalArgumentException("null iKeyFactory");
     }
-
     H = makeHeapModel();
   }
 
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/PointerKeyComparator.java b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/PointerKeyComparator.java
index f7c85c6e0..df0f50e63 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/PointerKeyComparator.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/PointerKeyComparator.java
@@ -25,6 +25,9 @@ public class PointerKeyComparator implements Comparator {
   private final IClassHierarchy cha;
 
   public PointerKeyComparator(IClassHierarchy cha) {
+    if (cha == null) {
+      throw new IllegalArgumentException("null cha");
+    }
     this.cha = cha;
   }
 
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/ContainerContextSelector.java b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/ContainerContextSelector.java
index ddd966f28..4476d0f68 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/ContainerContextSelector.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/ContainerContextSelector.java
@@ -84,8 +84,8 @@ public class ContainerContextSelector implements ContextSelector {
   public ContainerContextSelector(IClassHierarchy cha, ZeroXInstanceKeys delegate) {
     this.cha = cha;
     this.delegate = delegate;
-    if (Assertions.verifyAssertions) {
-      Assertions._assert(delegate != null);
+    if (delegate == null) {
+      throw new IllegalArgumentException("null delegate");
     }
   }
 
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/DefaultPointerKeyFactory.java b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/DefaultPointerKeyFactory.java
index 29046465b..0da2d30ad 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/DefaultPointerKeyFactory.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/DefaultPointerKeyFactory.java
@@ -61,8 +61,8 @@ public class DefaultPointerKeyFactory implements PointerKeyFactory {
   }
 
   public PointerKey getPointerKeyForStaticField(IField f) {
-    if (Assertions.verifyAssertions) {
-      Assertions._assert(f != null, "null f");
+    if (f == null) {
+      throw new IllegalArgumentException("null f");
     }
     return new StaticFieldKey(f);
   }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/ZeroXInstanceKeys.java b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/ZeroXInstanceKeys.java
index 5f15287be..b2fb519f8 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/ZeroXInstanceKeys.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/cfa/ZeroXInstanceKeys.java
@@ -319,8 +319,11 @@ public class ZeroXInstanceKeys implements InstanceKeyFactory {
         || C.getReference().equals(JavaLangStringBuilder) || C.getReference().equals(JavaLangAbstractStringBuilder);
   }
 
-  public static boolean isThrowable(IClass C) {
-    return C.getClassHierarchy().isSubclassOf(C, C.getClassHierarchy().lookupClass(TypeReference.JavaLangThrowable));
+  public static boolean isThrowable(IClass c) {
+    if (c == null) {
+      throw new IllegalArgumentException("null c");
+    }
+    return c.getClassHierarchy().isSubclassOf(c, c.getClassHierarchy().lookupClass(TypeReference.JavaLangThrowable));
   }
 
   public boolean isStackTraceElement(IClass C) {
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ipa/modref/DelegatingExtendedHeapModel.java b/com.ibm.wala.core/src/com/ibm/wala/ipa/modref/DelegatingExtendedHeapModel.java
index 07cbba9a0..a063328f8 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ipa/modref/DelegatingExtendedHeapModel.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ipa/modref/DelegatingExtendedHeapModel.java
@@ -26,13 +26,15 @@ import com.ibm.wala.types.TypeReference;
 /**
  * An implementation of {@link ExtendedHeapModel} based on a 
  * normal {@link HeapModel}
- *
  */
 public class DelegatingExtendedHeapModel implements ExtendedHeapModel {
 
    private final HeapModel h;
    
    public DelegatingExtendedHeapModel(HeapModel h) {
+     if (h == null) {
+       throw new IllegalArgumentException("null h");
+     }
      this.h = h;
    }
 
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ipa/slicer/thin/CISlicer.java b/com.ibm.wala.core/src/com/ibm/wala/ipa/slicer/thin/CISlicer.java
index 9d4b2f192..07e820698 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ipa/slicer/thin/CISlicer.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ipa/slicer/thin/CISlicer.java
@@ -104,6 +104,9 @@ public class CISlicer {
    * Compute the set of pointer keys each statement refs
    */
   public static Map<Statement, Set<PointerKey>> scanForRef(SDG sdg, PointerAnalysis pa) {
+    if (sdg == null) {
+      throw new IllegalArgumentException("null sdg");
+    }
     return scanForRef(sdg, pa, ModRef.make());
   }
 
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ipa/summaries/SyntheticIR.java b/com.ibm.wala.core/src/com/ibm/wala/ipa/summaries/SyntheticIR.java
index 33bb1f350..8d1062868 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ipa/summaries/SyntheticIR.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ipa/summaries/SyntheticIR.java
@@ -31,8 +31,8 @@ public class SyntheticIR extends IR {
   private final static boolean PARANOID = true;
 
   /**
-   * Create an SSA form, induced over a list of instructions provided externally. This entrypoint is often used for,
-   * e.g., native method models
+   * Create an SSA form, induced over a list of instructions provided externally. This entrypoint is often used for, e.g., native
+   * method models
    * 
    * @param method the method to construct SSA form for
    * @param context the governing context
@@ -72,7 +72,9 @@ public class SyntheticIR extends IR {
    */
   private static SymbolTable makeSymbolTable(IMethod method, SSAInstruction[] instructions, Map<Integer, ConstantValue> constants,
       AbstractCFG cfg) {
-    assert method != null;
+    if (method == null) {
+      throw new IllegalArgumentException("null method");
+    }
     SymbolTable symbolTable = new SymbolTable(method.getNumberOfParameters());
 
     // simulate allocation of value numbers
@@ -82,13 +84,12 @@ public class SyntheticIR extends IR {
         updateForInstruction(constants, symbolTable, s);
       }
     }
-    
+
     /**
-     * In InducedCFGs, we have nulled out phi instructions from the instruction array ... so go back and
-     * retrieve them now.
+     * In InducedCFGs, we have nulled out phi instructions from the instruction array ... so go back and retrieve them now.
      */
     if (cfg instanceof InducedCFG) {
-      InducedCFG icfg = (InducedCFG)cfg;
+      InducedCFG icfg = (InducedCFG) cfg;
       for (SSAPhiInstruction phi : icfg.getAllPhiInstructions()) {
         updateForInstruction(constants, symbolTable, phi);
       }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/model/java/lang/reflect/Array.java b/com.ibm.wala.core/src/com/ibm/wala/model/java/lang/reflect/Array.java
index 6a63a15d0..97be0641c 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/model/java/lang/reflect/Array.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/model/java/lang/reflect/Array.java
@@ -21,7 +21,6 @@ public class Array {
    */
   public static Object get(Object array, int index) throws IllegalArgumentException, ArrayIndexOutOfBoundsException {
 
-    
     if (!array.getClass().isArray()) {
       throw new IllegalArgumentException();
     }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ssa/NullTestPiPolicy.java b/com.ibm.wala.core/src/com/ibm/wala/ssa/NullTestPiPolicy.java
index 6b6641ef4..6b7b1252a 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ssa/NullTestPiPolicy.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ssa/NullTestPiPolicy.java
@@ -40,6 +40,9 @@ public class NullTestPiPolicy implements SSAPiNodePolicy {
     if (symbolTable == null) {
       throw new IllegalArgumentException("null symbolTable");
     }
+    if (cond == null) {
+      throw new IllegalArgumentException("null cond");
+    }
     if (symbolTable.isNullConstant(cond.getUse(1))) {
       return Pair.<Integer,SSAInstruction>make(cond.getUse(0), cond);
     }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ssa/SSAArrayLoadInstruction.java b/com.ibm.wala.core/src/com/ibm/wala/ssa/SSAArrayLoadInstruction.java
index febe2bc8a..d5d2225cc 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ssa/SSAArrayLoadInstruction.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ssa/SSAArrayLoadInstruction.java
@@ -13,14 +13,10 @@ package com.ibm.wala.ssa;
 import java.util.Collection;
 
 import com.ibm.wala.types.TypeReference;
-import com.ibm.wala.util.debug.Assertions;
 import com.ibm.wala.util.shrike.Exceptions;
 
 /**
  * SSA instruction representing an array load.
- * 
- * @author sfink
- * 
  */
 public class SSAArrayLoadInstruction extends SSAArrayReferenceInstruction {
   private final int result;
@@ -76,8 +72,8 @@ public class SSAArrayLoadInstruction extends SSAArrayReferenceInstruction {
 
   @Override
   public int getDef(int i) {
-    if (Assertions.verifyAssertions) {
-      Assertions._assert(i == 0);
+    if (i != 0) {
+      throw new IllegalArgumentException("illegal i: " + i);
     }
     return result;
   }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ssa/SSAArrayReferenceInstruction.java b/com.ibm.wala.core/src/com/ibm/wala/ssa/SSAArrayReferenceInstruction.java
index 650d6d633..efba88075 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ssa/SSAArrayReferenceInstruction.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ssa/SSAArrayReferenceInstruction.java
@@ -29,6 +29,9 @@ public abstract class SSAArrayReferenceInstruction extends SSAInstruction {
     this.arrayref = arrayref;
     this.index = index;
     this.elementType = elementType;
+    if (elementType == null) {
+      throw new IllegalArgumentException("null elementType");
+    }
   }
 
   /*
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ssa/SSAArrayStoreInstruction.java b/com.ibm.wala.core/src/com/ibm/wala/ssa/SSAArrayStoreInstruction.java
index b441e151d..fca490b0a 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ssa/SSAArrayStoreInstruction.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ssa/SSAArrayStoreInstruction.java
@@ -16,8 +16,6 @@ import com.ibm.wala.types.TypeReference;
 import com.ibm.wala.util.shrike.Exceptions;
 
 /**
- * @author sfink
- * 
  */
 public class SSAArrayStoreInstruction extends SSAArrayReferenceInstruction {
 
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ssa/SymbolTable.java b/com.ibm.wala.core/src/com/ibm/wala/ssa/SymbolTable.java
index 5a40116b1..c35315c02 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ssa/SymbolTable.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ssa/SymbolTable.java
@@ -197,6 +197,9 @@ public class SymbolTable {
   }
 
   public boolean isOne(int v) {
+    if (v < 0) {
+      throw new IllegalArgumentException("Illegal v: " + v);
+    }
     return (values[v] instanceof ConstantValue) && ((ConstantValue) values[v]).isOneConstant();
   }
 
diff --git a/com.ibm.wala.core/src/com/ibm/wala/types/Descriptor.java b/com.ibm.wala.core/src/com/ibm/wala/types/Descriptor.java
index 41177a61c..df1a84146 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/types/Descriptor.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/types/Descriptor.java
@@ -44,6 +44,9 @@ public final class Descriptor {
    * @return the canonical representative for this descriptor value
    */
   public static Descriptor findOrCreate(TypeName[] parameters, TypeName returnType) {
+    if (returnType == null) {
+      throw new IllegalArgumentException("null returnType");
+    }
     if (parameters != null && parameters.length == 0) {
       parameters = null;
     }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/types/Selector.java b/com.ibm.wala.core/src/com/ibm/wala/types/Selector.java
index 45a116c29..0d81df3ce 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/types/Selector.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/types/Selector.java
@@ -27,11 +27,15 @@ public final class Selector {
     if (selectorStr == null) {
       throw new IllegalArgumentException("null selectorStr");
     }
-    String methodName = selectorStr.substring(0, selectorStr.indexOf('('));
-    String desc = selectorStr.substring(selectorStr.indexOf('('));
-    return new Selector(Atom.findOrCreateUnicodeAtom(methodName), Descriptor.findOrCreateUTF8(desc));
-    
+    try {
+      String methodName = selectorStr.substring(0, selectorStr.indexOf('('));
+      String desc = selectorStr.substring(selectorStr.indexOf('('));
+      return new Selector(Atom.findOrCreateUnicodeAtom(methodName), Descriptor.findOrCreateUTF8(desc));
+    } catch (StringIndexOutOfBoundsException e) {
+      throw new IllegalArgumentException("invalid selectorStr: " + selectorStr);
+    }
   }
+
   public Selector(Atom name, Descriptor descriptor) {
     this.name = name;
     this.descriptor = descriptor;
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/collections/Filtersection.java b/com.ibm.wala.core/src/com/ibm/wala/util/collections/Filtersection.java
index 017a265e7..69331ed3b 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/collections/Filtersection.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/collections/Filtersection.java
@@ -13,10 +13,7 @@ package com.ibm.wala.util.collections;
 import com.ibm.wala.annotations.NonNull;
 
 /**
- *
  * intersection of two filters
- * 
- * @author sfink
  */
 public class Filtersection<T> implements Filter<T> {
   
@@ -27,6 +24,12 @@ public class Filtersection<T> implements Filter<T> {
   public Filtersection(Filter<T> a, Filter<T> b) {
     this.a = a;
     this.b = b;
+    if (a == null) {
+      throw new IllegalArgumentException("null a");
+    }
+    if (b == null) {
+      throw new IllegalArgumentException("null b");
+    }
   }
 
   public boolean accepts(T o) {
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/collections/HashMapFactory.java b/com.ibm.wala.core/src/com/ibm/wala/util/collections/HashMapFactory.java
index d0524bb26..0f0e94a0a 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/collections/HashMapFactory.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/collections/HashMapFactory.java
@@ -52,6 +52,9 @@ public class HashMapFactory {
    * @return A ParanoidHashMap if DEBUG = true, a LinkedHashMap otherwise
    */
   public static <K,V> HashMap<K,V> make(Map<K,V> t) {
+    if (t == null) {
+      throw new IllegalArgumentException("null t");
+    }
     if (HashSetFactory.DEBUG) {
       return new ParanoidHashMap<K,V>(t);
     } else {
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/collections/TwoLevelVector.java b/com.ibm.wala.core/src/com/ibm/wala/util/collections/TwoLevelVector.java
index a8d3401a9..bcb254dcd 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/collections/TwoLevelVector.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/collections/TwoLevelVector.java
@@ -68,6 +68,9 @@ public class TwoLevelVector<T> implements IVector<T> {
    * @see com.ibm.wala.util.intset.IntVector#set(int, int)
    */
   public void set(int x, T value) {
+    if (x < 0) {
+      throw new IllegalArgumentException("illegal x: " + x);
+    }
     int page = getPageNumber(x);
     IVector<T> v = findOrCreatePage(page);
     int localX = toLocalIndex(x, page);
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/config/AnalysisScopeReader.java b/com.ibm.wala.core/src/com/ibm/wala/util/config/AnalysisScopeReader.java
index 9357cf76c..3a4426b1d 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/config/AnalysisScopeReader.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/config/AnalysisScopeReader.java
@@ -85,6 +85,9 @@ public class AnalysisScopeReader {
   }
 
   public static void processScopeDefLine(AnalysisScope scope, ClassLoader javaLoader, String line) throws IOException {
+    if (line == null) {
+      throw new IllegalArgumentException("null line");
+    }
     StringTokenizer toks = new StringTokenizer(line, "\n,");
     if (!toks.hasMoreTokens()) {
       return;
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/intset/FixedSizeBitVector.java b/com.ibm.wala.core/src/com/ibm/wala/util/intset/FixedSizeBitVector.java
index dc0905f6b..01d08b58f 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/intset/FixedSizeBitVector.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/intset/FixedSizeBitVector.java
@@ -91,6 +91,9 @@ public final class FixedSizeBitVector implements Cloneable, java.io.Serializable
    * @param bit the bit to be cleared
    */
   public void clear(int bit) {
+    if (bit < 0) {
+      throw new IllegalArgumentException("illegal bit: " + bit);
+    }
     int shiftBits = bit & LOW_MASK;
     bits[subscript(bit)] &= ~(1 << shiftBits);
   }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/intset/IntSetUtil.java b/com.ibm.wala.core/src/com/ibm/wala/util/intset/IntSetUtil.java
index 7f79340e6..081111bab 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/intset/IntSetUtil.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/intset/IntSetUtil.java
@@ -117,6 +117,12 @@ public class IntSetUtil {
     if (factory == null) {
       throw new IllegalArgumentException("null factory");
     }
+    if (A == null) {
+      throw new IllegalArgumentException("null A");
+    }
+    if (B == null) {
+      throw new IllegalArgumentException("null B");
+    }
     if (A instanceof SparseIntSet && B instanceof SparseIntSet) {
       return SparseIntSet.diff((SparseIntSet) A, (SparseIntSet) B);
     } else if (A instanceof SemiSparseMutableIntSet && B instanceof SemiSparseMutableIntSet) {
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/intset/MutableSparseIntSet.java b/com.ibm.wala.core/src/com/ibm/wala/util/intset/MutableSparseIntSet.java
index 956945c06..677859c22 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/intset/MutableSparseIntSet.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/intset/MutableSparseIntSet.java
@@ -423,6 +423,9 @@ public class MutableSparseIntSet extends SparseIntSet implements MutableIntSet {
   }
 
   public <T extends BitVectorBase<T>> void removeAll(T v) {
+    if (v == null) {
+      throw new IllegalArgumentException("null v");
+    }
     int ai = 0;
     for (int i = 0; i < size; i++) {
       if (!v.get(elements[i])) {
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/intset/SparseIntSet.java b/com.ibm.wala.core/src/com/ibm/wala/util/intset/SparseIntSet.java
index d7954f209..4cdeee93d 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/intset/SparseIntSet.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/intset/SparseIntSet.java
@@ -138,6 +138,9 @@ public class SparseIntSet implements IntSet {
   }
 
   public final int elementAt(int idx) throws NoSuchElementException {
+    if (idx < 0) {
+      throw new IllegalArgumentException("invalid idx: " + idx);
+    }
     if (elements == null || idx >= size) {
       throw new NoSuchElementException("Index: " + idx);
     }
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 aa2f9f542..aa8488559 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
@@ -386,6 +386,9 @@ public class SparseLongSet implements LongSet {
   }
 
   public void foreach(LongSetAction action) {
+    if (action == null) {
+      throw new IllegalArgumentException("null action");
+    }
     for (int i = 0; i < size; i++)
       action.act(elements[i]);
   }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/io/CommandLine.java b/com.ibm.wala.core/src/com/ibm/wala/util/io/CommandLine.java
index d385786ee..bc24d7156 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/io/CommandLine.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/io/CommandLine.java
@@ -33,6 +33,10 @@ public class CommandLine {
     }
     Properties result = new Properties();
     for (int i = 0; i < args.length; i++) {
+      if (args[i] == null) {
+        // skip it
+        continue;
+      }
       String key = parseForKey(args[i]);
       if (key != null) {
         if (args[i].contains("=")) {
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/io/FileProvider.java b/com.ibm.wala.core/src/com/ibm/wala/util/io/FileProvider.java
index b7e869d04..e0dd091b6 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/io/FileProvider.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/io/FileProvider.java
@@ -95,6 +95,9 @@ public class FileProvider {
   }
 
   public static URL getResource(String fileName, ClassLoader loader) throws IOException {
+    if (CorePlugin.getDefault() == null && loader == null) {
+      throw new IllegalArgumentException("null loader");
+    }
     return (CorePlugin.getDefault() == null) ? loader.getResource(fileName) : FileLocator.find(CorePlugin.getDefault().getBundle(),
         new Path(fileName), null);
   }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/strings/ImmutableByteArray.java b/com.ibm.wala.core/src/com/ibm/wala/util/strings/ImmutableByteArray.java
index e0507bd28..59867d003 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/strings/ImmutableByteArray.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/strings/ImmutableByteArray.java
@@ -10,13 +10,8 @@
  *******************************************************************************/
 package com.ibm.wala.util.strings;
 
-import com.ibm.wala.util.debug.Assertions;
-
 /**
- * 
  * A read-only byte array.
- * 
- * @author sfink
  */
 public final class ImmutableByteArray {
 
@@ -34,10 +29,10 @@ public final class ImmutableByteArray {
     if (b == null) {
       throw new IllegalArgumentException("b is null");
     }
-    this.b = new byte[length];
-    if (Assertions.verifyAssertions) {
-      Assertions._assert(b.length >= start + length, "illegal");
+    if (start < 0) {
+      throw new IllegalArgumentException("invalid start: " + start);
     }
+    this.b = new byte[length];
     System.arraycopy(b, start, this.b, 0, length);
   }
 
diff --git a/com.ibm.wala.core/src/com/ibm/wala/viz/GVUtil.java b/com.ibm.wala.core/src/com/ibm/wala/viz/GVUtil.java
index f98fc75fc..ff2aec517 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/viz/GVUtil.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/viz/GVUtil.java
@@ -27,6 +27,9 @@ public class GVUtil {
     if (gvExe == null) {
       throw new IllegalArgumentException("null gvExe");
     }
+    if (psFile == null) {
+      throw new IllegalArgumentException("null psFile");
+    }
     final GSViewLauncher gv = new GSViewLauncher();
     gv.setGvExe(gvExe);
     gv.setPsfile(psFile);
diff --git a/com.ibm.wala.core/src/com/ibm/wala/viz/ViewIFDSLocalAction.java b/com.ibm.wala.core/src/com/ibm/wala/viz/ViewIFDSLocalAction.java
index 6526980ea..2900ba6f9 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/viz/ViewIFDSLocalAction.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/viz/ViewIFDSLocalAction.java
@@ -85,6 +85,9 @@ public class ViewIFDSLocalAction<T, P, F> extends Action {
 
   public ViewIFDSLocalAction(SWTTreeViewer viewer, TabulationResult<T, P, F> result, String psFile, String dotFile, String dotExe,
       String gvExe) {
+    if (result == null) {
+      throw new IllegalArgumentException("null result");
+    }
     this.viewer = viewer;
     this.supergraph = result.getProblem().getSupergraph();
     this.psFile = psFile;