diff --git a/com.ibm.wala.core/src/com/ibm/wala/demandpa/genericutil/ArraySet.java b/com.ibm.wala.core/src/com/ibm/wala/demandpa/genericutil/ArraySet.java
index 08fc445ae..b6426bb3e 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/demandpa/genericutil/ArraySet.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/demandpa/genericutil/ArraySet.java
@@ -55,6 +55,9 @@ public class ArraySet<T> extends AbstractSet<T> {
 
   private static final ArraySet EMPTY = new ArraySet<Object>(0, true) {
     @Override
+    /**
+     * @throws UnsupportedOperationException unconditionally
+     */
     public boolean add(Object obj_) {
       throw new UnsupportedOperationException();
     }
diff --git a/com.ibm.wala.core/src/com/ibm/wala/dynamic/JavaLauncher.java b/com.ibm.wala.core/src/com/ibm/wala/dynamic/JavaLauncher.java
index 8358ca89c..0a53c45cf 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/dynamic/JavaLauncher.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/dynamic/JavaLauncher.java
@@ -179,6 +179,7 @@ public class JavaLauncher extends Launcher {
 
   /**
    * Wait for the spawned process to terminate.
+   * @throws IllegalStateException if the process has not been started
    */
   public void join() {
     if (stdOutDrain == null || stdErrDrain == null) {
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/PointsToMap.java b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/PointsToMap.java
index b8a35341f..9c26d640f 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/PointsToMap.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/PointsToMap.java
@@ -133,6 +133,9 @@ public class PointsToMap {
    * record that a particular points-to-set has been unioned with another
    */
   public void recordUnified(PointerKey key) {
+    if (key == null) {
+      throw new IllegalArgumentException("null key");
+    }
     int i = findOrCreateIndex(key);
     pointsToSets.set(i, UNIFIED);
   }
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 63b16e91f..f8b0142c1 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
@@ -19,8 +19,8 @@ import com.ibm.wala.util.debug.Assertions;
  * By convention, symbol numbers start at 1 ... the "this" parameter will be symbol number 1 in a virtual method.
  */
 public class SymbolTable {
-  
-  private final static int MAX_VALUE_NUMBER = Integer.MAX_VALUE/4;
+
+  private final static int MAX_VALUE_NUMBER = Integer.MAX_VALUE / 4;
 
   /**
    * value numbers for parameters to this method
@@ -88,9 +88,16 @@ public class SymbolTable {
     }
   }
 
+  /**
+   * set the default value for a value number.
+   * 
+   * @throws IllegalStateException if that value number value is already assigned
+   */
   public void setDefaultValue(int vn, final Object defaultValue) {
     try {
-      Assertions._assert(values[vn] == null);
+      if (values[vn] != null) {
+        throw new IllegalStateException("cannot set default value of vn " + vn);
+      }
 
       values[vn] = new Value() {
         public boolean isStringConstant() {
@@ -185,7 +192,7 @@ public class SymbolTable {
       }
     } catch (ArrayIndexOutOfBoundsException e) {
       throw new IllegalArgumentException("invalid i: " + i);
-    } 
+    }
 
   }
 
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 081111bab..971b0c134 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
@@ -51,8 +51,12 @@ public class IntSetUtil {
    * 
    * @param set
    * @return a new MutableIntSet object with the same value as set
-   * @throws UnimplementedError  if (not ( set instanceof com.ibm.wala.util.intset.SparseIntSet ) ) and (not ( set instanceof com.ibm.wala.util.intset.BitVectorIntSet ) ) and (not ( set instanceof com.ibm.wala.util.intset.BimodalMutableIntSet ) ) and (not ( set instanceof com.ibm.wala.util.intset.DebuggingMutableIntSet ) ) and (not ( set instanceof com.ibm.wala.util.intset.SemiSparseMutableIntSet ) ) and (not ( set instanceof com.ibm.wala.util.intset.MutableSharedBitVectorIntSet ) )
-   * @throws IllegalArgumentException  if set == null
+   * @throws UnimplementedError if (not ( set instanceof com.ibm.wala.util.intset.SparseIntSet ) ) and (not ( set instanceof
+   *           com.ibm.wala.util.intset.BitVectorIntSet ) ) and (not ( set instanceof com.ibm.wala.util.intset.BimodalMutableIntSet
+   *           ) ) and (not ( set instanceof com.ibm.wala.util.intset.DebuggingMutableIntSet ) ) and (not ( set instanceof
+   *           com.ibm.wala.util.intset.SemiSparseMutableIntSet ) ) and (not ( set instanceof
+   *           com.ibm.wala.util.intset.MutableSharedBitVectorIntSet ) )
+   * @throws IllegalArgumentException if set == null
    */
   public static MutableIntSet makeMutableCopy(IntSet set) throws IllegalArgumentException, UnimplementedError {
     if (set == null) {
@@ -136,7 +140,7 @@ public class IntSetUtil {
   /**
    * Subtract two sets, i.e. a = a \ b.
    * 
-   * @throws IllegalArgumentException  if B == null
+   * @throws IllegalArgumentException if B == null
    */
   public static MutableIntSet removeAll(MutableIntSet A, IntSet B) throws IllegalArgumentException {
     if (B == null) {
@@ -175,8 +179,8 @@ public class IntSetUtil {
     if (low <= high && (low < 0 || high < 0)) {
       throw new IllegalArgumentException("can't search negative indices " + low + " " + high);
     }
-    if (high > data.length -1 ) {
-      high = data.length -1;
+    if (high > data.length - 1) {
+      high = data.length - 1;
     }
     if (low <= high) {
       int mid = (low + high) / 2;
@@ -201,16 +205,18 @@ public class IntSetUtil {
   }
 
   /**
-   * @param defaultIntSetFactory
-   *          The defaultIntSetFactory to set.
+   * @param defaultIntSetFactory The defaultIntSetFactory to set.
    */
   public static void setDefaultIntSetFactory(MutableIntSetFactory defaultIntSetFactory) {
+    if (defaultIntSetFactory == null) {
+      throw new IllegalArgumentException("null defaultIntSetFactory");
+    }
     IntSetUtil.defaultIntSetFactory = defaultIntSetFactory;
   }
 
   /**
    * @return a new sparse int set which adds j to s
-   * @throws IllegalArgumentException  if s == null
+   * @throws IllegalArgumentException if s == null
    */
   public static IntSet add(IntSet s, int j) throws IllegalArgumentException {
     if (s == null) {
@@ -220,7 +226,7 @@ public class IntSetUtil {
       SparseIntSet sis = (SparseIntSet) s;
       return SparseIntSet.add(sis, j);
     } else {
-      // really slow.  optimize as needed.
+      // really slow. optimize as needed.
       MutableSparseIntSet result = MutableSparseIntSet.make(s);
       result.add(j);
       return result;
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/intset/MutableSparseIntSetFactory.java b/com.ibm.wala.core/src/com/ibm/wala/util/intset/MutableSparseIntSetFactory.java
index 9a3ad614f..fc1cbd963 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/intset/MutableSparseIntSetFactory.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/intset/MutableSparseIntSetFactory.java
@@ -22,7 +22,6 @@ import java.util.TreeSet;
 public class MutableSparseIntSetFactory implements MutableIntSetFactory {
 
   /**
-   * @param set
    * @throws IllegalArgumentException  if set is null
    */
   public MutableIntSet make(int[] set) {
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/intset/OrdinalSet.java b/com.ibm.wala.core/src/com/ibm/wala/util/intset/OrdinalSet.java
index 119f8e116..dcd68af9c 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/intset/OrdinalSet.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/intset/OrdinalSet.java
@@ -182,6 +182,9 @@ public class OrdinalSet<T> implements Iterable<T> {
     if (c == null) {
       throw new IllegalArgumentException("c is null");
     }
+    if (m == null) {
+      throw new IllegalArgumentException("m is null");
+    }
     MutableSparseIntSet s = MutableSparseIntSet.makeEmpty();
     for (Iterator<T> it = c.iterator(); it.hasNext();) {
       int index = m.getMappedIndex(it.next());
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/io/FileUtil.java b/com.ibm.wala.core/src/com/ibm/wala/util/io/FileUtil.java
index eb6fc713b..4c5e82a0a 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/io/FileUtil.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/io/FileUtil.java
@@ -161,10 +161,16 @@ public class FileUtil {
     return new FileOutputStream(f);
   }
 
+  /**
+   * read fully the contents of s and return a byte array holding the result
+   * @throws IOException
+   */
   public static byte[] readBytes(InputStream s) throws IOException {
-    byte[] b;
+    if (s == null) {
+      throw new IllegalArgumentException("null s");
+    }
     ByteArrayOutputStream out = new ByteArrayOutputStream();
-    b = new byte[1024];
+    byte[] b = new byte[1024];
     int n = s.read(b);
     while (n != -1) {
       out.write(b, 0, n);
diff --git a/com.ibm.wala.core/src/com/ibm/wala/util/strings/Atom.java b/com.ibm.wala.core/src/com/ibm/wala/util/strings/Atom.java
index ec51a5892..949c45062 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/util/strings/Atom.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/util/strings/Atom.java
@@ -236,6 +236,7 @@ public final class Atom implements Serializable {
    * "[Ljava/lang/String;" or "[[I"
    * 
    * @return dimensionality - something like "1" or "2"
+   * @throws IllegalStateException if this Atom does not represent an array
    */
   public final int parseForArrayDimensionality() throws IllegalArgumentException {
     if (val.length == 0) {
@@ -255,6 +256,8 @@ public final class Atom implements Serializable {
 
   /**
    * Return the innermost element type reference for an array
+   * 
+   * @throws IllegalStateException if this Atom does not represent an array descriptor
    */
   public final Atom parseForInnermostArrayElementDescriptor() throws IllegalArgumentException {
     if (val.length == 0) {