minor improvements to ExceptionalUnitGraph and ThrowableSet

src/main/java/soot/toolkits/exceptions/ThrowableSet.java

@@ -87,11 +87,15 @@
  * with a given name.
  * </p>
  */
-
 public class ThrowableSet {
 
   private static final boolean INSTRUMENTING = false;
-  private final SootClass JAVA_LANG_OBJECT_CLASS = Scene.v().getObjectType().getSootClass();
+
+  // This pattern allows for the field to be static but to delay it's
+  // initialization until it's first use.
+  private static final class LazyInit {
+    static final SootClass JAVA_LANG_OBJECT_CLASS = Scene.v().getObjectType().getSootClass();
+  }
 
   /**
    * Set of exception types included within the set.
@@ -121,24 +125,23 @@ public class ThrowableSet {
    * @param exclude
    *          The set of {@link AnySubType} objects representing the types to be excluded from the set.
    */
-  protected ThrowableSet(Set<RefLikeType> include, Set<AnySubType> exclude) {
+  private ThrowableSet(Set<RefLikeType> include, Set<AnySubType> exclude) {
     exceptionsIncluded = getImmutable(include);
     exceptionsExcluded = getImmutable(exclude);
-    // We don't need to clone include and exclude to guarantee
-    // immutability since ThrowableSet(Set,Set) is private to this
-    // class, where it is only called (via
-    // Manager.v().registerSetIfNew()) with arguments which the
+    // We don't need to clone include and exclude to guarantee immutability
+    // since ThrowableSet(Set,Set) is private to this class, where it is only
+    // called (via Manager.v().registerSetIfNew()) with arguments which the
     // callers do not subsequently modify.
   }
 
   private static <T> Set<T> getImmutable(Set<T> in) {
-    if ((null == in) || in.isEmpty()) {
+    if (in == null || in.isEmpty()) {
       return Collections.emptySet();
-    }
-    if (1 == in.size()) {
+    } else if (in.size() == 1) {
       return Collections.singleton(in.iterator().next());
+    } else {
+      return Collections.unmodifiableSet(in);
     }
-    return Collections.unmodifiableSet(in);
   }
 
   /**
@@ -201,9 +204,9 @@ private void addToMemoizedAdds(Object key, ThrowableSet value) {
    *
    * @return a set containing <code>e</code> as well as the exceptions in this set.
    *
-   * @throws {@link
-   *           ThrowableSet.IllegalStateException} if this <code>ThrowableSet</code> is the result of a
-   *           {@link #whichCatchableAs(RefType)} operation and, thus, unable to represent the addition of <code>e</code>.
+   * @throws IllegalStateException
+   *           if this <code>ThrowableSet</code> is the result of a {@link #whichCatchableAs(RefType)} operation and, thus,
+   *           unable to represent the addition of <code>e</code>.
    */
   public ThrowableSet add(RefType e) throws ThrowableSet.AlreadyHasExclusionsException {
     if (INSTRUMENTING) {
@@ -275,7 +278,7 @@ public ThrowableSet add(RefType e) throws ThrowableSet.AlreadyHasExclusionsExcep
 
   private boolean hasNoHierarchy(RefType type) {
     final SootClass sootClass = type.getSootClass();
-    return !(sootClass.hasSuperclass() || JAVA_LANG_OBJECT_CLASS == sootClass);
+    return !(sootClass.hasSuperclass() || LazyInit.JAVA_LANG_OBJECT_CLASS == sootClass);
   }
 
   /**
@@ -535,14 +538,7 @@ private ThrowableSet add(Set<RefLikeType> addedExceptions) {
         }
       }
     }
-
-    ThrowableSet result = null;
-    if (changes > 0) {
-      result = Manager.v().registerSetIfNew(resultSet, this.exceptionsExcluded);
-    } else {
-      result = this;
-    }
-    return result;
+    return (changes > 0) ? Manager.v().registerSetIfNew(resultSet, this.exceptionsExcluded) : this;
   }
 
   /**
@@ -570,14 +566,7 @@ private ThrowableSet remove(Set<RefLikeType> removedExceptions) {
         }
       }
     }
-
-    ThrowableSet result = null;
-    if (changes > 0) {
-      result = Manager.v().registerSetIfNew(resultSet, this.exceptionsExcluded);
-    } else {
-      result = this;
-    }
-    return result;
+    return (changes > 0) ? Manager.v().registerSetIfNew(resultSet, this.exceptionsExcluded) : this;
   }
 
   /**
@@ -646,7 +635,7 @@ public boolean catchableAs(RefType catcher) {
 
     if (exceptionsIncluded.contains(catcher)) {
       if (INSTRUMENTING) {
-        if (exceptionsExcluded.size() == 0) {
+        if (exceptionsExcluded.isEmpty()) {
           Manager.v().catchableAsFromMap++;
         } else {
           Manager.v().catchableAsFromSearch++;
@@ -655,7 +644,7 @@ public boolean catchableAs(RefType catcher) {
       return true;
     } else {
       if (INSTRUMENTING) {
-        if (exceptionsExcluded.size() == 0) {
+        if (exceptionsExcluded.isEmpty()) {
           Manager.v().catchableAsFromSearch++;
         }
       }
@@ -671,13 +660,11 @@ public boolean catchableAs(RefType catcher) {
         } else {
           RefType thrownBase = ((AnySubType) thrownType).getBase();
           if (catcherHasNoHierarchy) {
-            if (thrownBase.equals(catcher) || thrownBase.getClassName().equals("java.lang.Throwable")) {
+            if (thrownBase.equals(catcher) || "java.lang.Throwable".equals(thrownBase.getClassName())) {
               return true;
             }
-          }
-          // At runtime, thrownType might be instantiated by any
-          // of thrownBase's subtypes, so:
-          else if (h.canStoreType(thrownBase, catcher) || h.canStoreType(catcher, thrownBase)) {
+          } else if (h.canStoreType(thrownBase, catcher) || h.canStoreType(catcher, thrownBase)) {
+            // At runtime, thrownType might be instantiated by any of thrownBase's subtypes
             return true;
           }
         }
@@ -760,7 +747,7 @@ public Pair whichCatchableAs(RefType catcher) {
           if (base.equals(catcher)) {
             caughtIncluded = addExceptionToSet(inclusion, caughtIncluded);
           } else {
-            if (base.getClassName().equals("java.lang.Throwable")) {
+            if ("java.lang.Throwable".equals(base.getClassName())) {
               caughtIncluded = addExceptionToSet(catcher, caughtIncluded);
             }
             uncaughtIncluded = addExceptionToSet(inclusion, uncaughtIncluded);
@@ -818,7 +805,7 @@ private <T> Set<T> addExceptionToSet(T e, Set<T> set) {
    */
   @Override
   public String toString() {
-    StringBuffer buffer = new StringBuffer(this.toBriefString());
+    StringBuilder buffer = new StringBuilder(this.toBriefString());
     buffer.append(":\n  ");
     for (RefLikeType ei : exceptionsIncluded) {
       buffer.append('+');
@@ -882,7 +869,7 @@ private String toAbbreviatedString(Set<? extends RefLikeType> s, char connector)
 
     Collection<RefLikeType> vmErrorThrowables = ThrowableSet.Manager.v().VM_ERRORS.exceptionsIncluded;
     boolean containsAllVmErrors = s.containsAll(vmErrorThrowables);
-    StringBuffer buf = new StringBuffer();
+    StringBuilder buf = new StringBuilder();
 
     if (containsAllVmErrors) {
       buf.append(connector);
@@ -1161,7 +1148,8 @@ public static Manager v() {
      * @return a <code>ThrowableSet</code> representing the set of exceptions corresponding to <code>include</code> -
      *         <code>exclude</code>.
      */
-    protected ThrowableSet registerSetIfNew(Set<RefLikeType> include, Set<AnySubType> exclude) {
+    private ThrowableSet registerSetIfNew(Set<RefLikeType> include, Set<AnySubType> exclude) {
+      //NOTE: This method must be private in accordance with the comment in the ThrowableSet constructor.
       if (INSTRUMENTING) {
         registrationCalls++;
       }
@@ -1181,9 +1169,7 @@ protected ThrowableSet registerSetIfNew(Set<RefLikeType> include, Set<AnySubType
      * @return a string listing the counts.
      */
     public String reportInstrumentation() {
-      int setCount = registry.size();
-
-      StringBuffer buf = new StringBuffer("registeredSets: ").append(setCount).append("\naddsOfRefType: ")
+      StringBuilder buf = new StringBuilder("registeredSets: ").append(registry.size()).append("\naddsOfRefType: ")
           .append(addsOfRefType).append("\naddsOfAnySubType: ").append(addsOfAnySubType).append("\naddsOfSet: ")
           .append(addsOfSet).append("\naddsInclusionFromMap: ").append(addsInclusionFromMap)
           .append("\naddsInclusionFromMemo: ").append(addsInclusionFromMemo).append("\naddsInclusionFromSearch: ")
@@ -1218,8 +1204,9 @@ public AlreadyHasExclusionsException(String s) {
    * The return type for {@link ThrowableSet#whichCatchableAs(RefType)}, consisting of a pair of ThrowableSets.
    */
   public static class Pair {
-    private ThrowableSet caught;
-    private ThrowableSet uncaught;
+
+    private final ThrowableSet caught;
+    private final ThrowableSet uncaught;
 
     /**
      * Constructs a <code>ThrowableSet.Pair</code>.
@@ -1270,10 +1257,7 @@ public boolean equals(Object o) {
         return false;
       }
       Pair tsp = (Pair) o;
-      if (this.caught.equals(tsp.caught) && this.uncaught.equals(tsp.uncaught)) {
-        return true;
-      }
-      return false;
+      return this.caught.equals(tsp.caught) && this.uncaught.equals(tsp.uncaught);
     }
 
     @Override
@@ -1287,7 +1271,6 @@ public int hashCode() {
 
   /**
    * Comparator used to implement sortedThrowableIterator().
-   *
    */
   private static class ThrowableComparator<T extends RefLikeType> implements java.util.Comparator<T> {
 
@@ -1322,6 +1305,5 @@ public int compare(T o1, T o2) {
         return t1.toString().compareTo(t2.toString());
       }
     }
-
   }
 }

src/main/java/soot/toolkits/graph/ExceptionalUnitGraph.java

@@ -255,47 +255,50 @@ protected void initialize(ThrowAnalysis throwAnalysis, boolean omitExceptingUnit
    *         extending <code>ExceptionalUnitGraph</code>. If a <code>Unit</code> throws one or more exceptions which are
    *         caught within the method, it will be mapped to a <code>Collection</code> of <code>ExceptionDest</code>s
    *         describing the sets of exceptions that the <code>Unit</code> might throw to each {@link Trap}. But if all of a
-   *         <code>Unit</code>'s exceptions escape the method, it will be mapped to <code>null</code, rather than to a
+   *         <code>Unit</code>'s exceptions escape the method, it will be mapped to <code>null</code>, rather than to a
    *         <code>Collection</code> containing a single <code>ExceptionDest</code> with a <code>null</code> trap. (The
    *         special case for <code>Unit</code>s with no caught exceptions allows <code>buildExceptionDests()</code> to
    *         ignore completely <code>Unit</code>s which are outside the scope of all <code>Trap</code>s.)
    *         </p>
    */
   protected Map<Unit, Collection<ExceptionDest>> buildExceptionDests(ThrowAnalysis throwAnalysis) {
-    Chain<Unit> units = body.getUnits();
-    Map<Unit, ThrowableSet> unitToUncaughtThrowables = new LinkedHashMap<Unit, ThrowableSet>(units.size());
     Map<Unit, Collection<ExceptionDest>> result = null;
 
-    // Record the caught exceptions.
-    for (Trap trap : body.getTraps()) {
-      RefType catcher = trap.getException().getType();
-      for (Iterator<Unit> unitIt = units.iterator(trap.getBeginUnit(), units.getPredOf(trap.getEndUnit())); unitIt
-          .hasNext();) {
-        Unit unit = unitIt.next();
-        ThrowableSet thrownSet = unitToUncaughtThrowables.get(unit);
-        if (thrownSet == null) {
-          thrownSet = throwAnalysis.mightThrow(unit);
-        }
+    final Chain<Trap> traps = body.getTraps();
+    if (!traps.isEmpty()) {
+      final ThrowableSet EMPTY = ThrowableSet.Manager.v().EMPTY;
+      final Chain<Unit> units = body.getUnits();
+      final Map<Unit, ThrowableSet> unitToUncaughtThrowables = new LinkedHashMap<Unit, ThrowableSet>(units.size());
+
+      // Record the caught exceptions.
+      for (Trap trap : traps) {
+        RefType catcher = trap.getException().getType();
+        for (Iterator<Unit> it = units.iterator(trap.getBeginUnit(), units.getPredOf(trap.getEndUnit())); it.hasNext();) {
+          Unit unit = it.next();
+          ThrowableSet thrownSet = unitToUncaughtThrowables.get(unit);
+          if (thrownSet == null) {
+            thrownSet = throwAnalysis.mightThrow(unit);
+          }
 
-        ThrowableSet.Pair catchableAs = thrownSet.whichCatchableAs(catcher);
-        if (!catchableAs.getCaught().equals(ThrowableSet.Manager.v().EMPTY)) {
-          result = addDestToMap(result, unit, trap, catchableAs.getCaught());
-          unitToUncaughtThrowables.put(unit, catchableAs.getUncaught());
-        } else {
-          assert thrownSet.equals(catchableAs.getUncaught()) : "ExceptionalUnitGraph.buildExceptionDests(): "
-              + "catchableAs.caught == EMPTY, but catchableAs.uncaught != thrownSet" + System.getProperty("line.separator")
-              + body.getMethod().getSubSignature() + " Unit: " + unit.toString() + System.getProperty("line.separator")
-              + " catchableAs.getUncaught() == " + catchableAs.getUncaught().toString()
-              + System.getProperty("line.separator") + " thrownSet == " + thrownSet.toString();
+          ThrowableSet.Pair catchableAs = thrownSet.whichCatchableAs(catcher);
+          if (!EMPTY.equals(catchableAs.getCaught())) {
+            result = addDestToMap(result, unit, trap, catchableAs.getCaught());
+            unitToUncaughtThrowables.put(unit, catchableAs.getUncaught());
+          } else {
+            assert thrownSet.equals(catchableAs.getUncaught()) : "ExceptionalUnitGraph.buildExceptionDests(): "
+                + "catchableAs.caught == EMPTY, but catchableAs.uncaught != thrownSet" + System.getProperty("line.separator")
+                + body.getMethod().getSubSignature() + " Unit: " + unit.toString() + System.getProperty("line.separator")
+                + " catchableAs.getUncaught() == " + catchableAs.getUncaught().toString()
+                + System.getProperty("line.separator") + " thrownSet == " + thrownSet.toString();
+          }
         }
       }
-    }
 
-    for (Map.Entry<Unit, ThrowableSet> entry : unitToUncaughtThrowables.entrySet()) {
-      Unit unit = entry.getKey();
-      ThrowableSet escaping = entry.getValue();
-      if (escaping != ThrowableSet.Manager.v().EMPTY) {
-        result = addDestToMap(result, unit, null, escaping);
+      for (Map.Entry<Unit, ThrowableSet> entry : unitToUncaughtThrowables.entrySet()) {
+        ThrowableSet escaping = entry.getValue();
+        if (escaping != EMPTY) {
+          result = addDestToMap(result, entry.getKey(), null, escaping);
+        }
       }
     }
     return result == null ? Collections.emptyMap() : result;
@@ -322,8 +325,8 @@ protected Map<Unit, Collection<ExceptionDest>> buildExceptionDests(ThrowAnalysis
    * @return a <code>Map</code> which whose contents are equivalent to the input <code>map</code>, plus the information that
    *         <code>u</code> throws <code>caught</code> to <code>t</code>.
    */
-  private Map<Unit, Collection<ExceptionDest>> addDestToMap(Map<Unit, Collection<ExceptionDest>> map, Unit u, Trap t,
-      ThrowableSet caught) {
+  protected Map<Unit, Collection<ExceptionDest>> addDestToMap(Map<Unit, Collection<ExceptionDest>> map, Unit u,
+      Trap t, ThrowableSet caught) {
     Collection<ExceptionDest> dests = (map == null ? null : map.get(u));
     if (dests == null) {
       if (t == null) {
@@ -546,7 +549,7 @@ public int hashCode() {
   /**
    * <p>
    * Utility method for checking if a {@link Unit} might have side effects. It simply returns true for any unit which invokes
-   * a method directly or which might invoke static initializers indirectly (by creating a new object or by refering to a
+   * a method directly or which might invoke static initializers indirectly (by creating a new object or by referring to a
    * static field; see sections 2.17.4, 2.17.5, and 5.5 of the Java Virtual Machine Specification).
    * </p>
    *
@@ -667,8 +670,6 @@ public Collection<ExceptionDest> getExceptionDests(final Unit u) {
     Collection<ExceptionDest> result = unitToExceptionDests.get(u);
     if (result == null) {
       ExceptionDest e = new ExceptionDest(null, null) {
-        private ThrowableSet throwables;
-
         @Override
         public ThrowableSet getThrowables() {
           if (null == throwables) {
@@ -677,14 +678,14 @@ public ThrowableSet getThrowables() {
           return throwables;
         }
       };
-      return Collections.singletonList(e);
+      result = Collections.singletonList(e);
     }
     return result;
   }
 
   public static class ExceptionDest implements ExceptionalGraph.ExceptionDest<Unit> {
-    private Trap trap;
-    private ThrowableSet throwables;
+    private final Trap trap;
+    ThrowableSet throwables;
 
     protected ExceptionDest(Trap trap, ThrowableSet throwables) {
       this.trap = trap;
@@ -712,7 +713,7 @@ public Unit getHandlerNode() {
 
     @Override
     public String toString() {
-      StringBuffer buf = new StringBuffer();
+      StringBuilder buf = new StringBuilder();
       buf.append(getThrowables());
       buf.append(" -> ");
       if (trap == null) {