start to make UseVarArgs more usable

Author: mebigfatguy

etc/messages.xml

@@ -1173,9 +1173,13 @@ a[0] = new A(); // results in ArrayStoreException (Runtime)
 	<Detector class="com.mebigfatguy.fbcontrib.detect.UseVarArgs">
 		<Details>
 			<![CDATA[
-			<p>This detector looks for definitions of methods that have an array as the last parameter.
+			<p>This detector looks for problems and possibilities to use var args better. Specially looks for 
+			<ul>
+			<li>definitions of methods that have an array as the last parameter.
 			Since this class is compiled with Java 1.5 or better, it would be more flexible for clients of this
-			method to define this parameter as a vararg parameter.</p>
+			method to define this parameter as a vararg parameter</li>
+			<li>classes that have samed named vararg and non vararg methods not clearly differentiated.</li>
+			<li>Explicitly passing null to a var arg parameter</li></ul>.</p>
 			<p>It is a fast detector.</p>
 			]]>
 		</Details>

src/main/java/com/mebigfatguy/fbcontrib/detect/UseVarArgs.java

@@ -85,49 +85,55 @@ public void visitMethod(Method obj) {
 				return;
 			}
 
-			if (Values.CONSTRUCTOR.equals(getMethodName()) && javaClass.getClassName().contains("$")) {
-				return;
-			}
-
-			List<String> types = SignatureUtils.getParameterSignatures(obj.getSignature());
-			if ((types.isEmpty()) || (types.size() > 2)) {
-				return;
-			}
+			boolean isVarMethod  = (obj.getAccessFlags() & Constants.ACC_VARARGS) != 0;
 
-			if ((obj.getAccessFlags() & Constants.ACC_VARARGS) != 0) {
-				return;
-			}
+			boolean isConvertable = !isVarMethod && methodHasConvertableLastParam(obj);
 
-			String lastParmSig = types.get(types.size() - 1);
-			if (!lastParmSig.startsWith(Values.SIG_ARRAY_PREFIX)
-					|| lastParmSig.startsWith(Values.SIG_ARRAY_OF_ARRAYS_PREFIX)) {
-				return;
+			super.visitMethod(obj);
+			
+			if (isConvertable) {
+				bugReporter.reportBug(new BugInstance(this, BugType.UVA_USE_VAR_ARGS.name(), LOW_PRIORITY).addClass(this)
+					.addMethod(this));
 			}
 
-			if (SignatureBuilder.SIG_BYTE_ARRAY.equals(lastParmSig)
-					|| SignatureBuilder.SIG_CHAR_ARRAY.equals(lastParmSig)) {
-				return;
-			}
+		} catch (ClassNotFoundException cnfe) {
+			bugReporter.reportMissingClass(cnfe);
+		}
+	}
+	
+	public boolean methodHasConvertableLastParam(Method method) throws ClassNotFoundException {
+		if (Values.CONSTRUCTOR.equals(getMethodName()) && javaClass.getClassName().contains("$")) {
+			return false;
+		}
+		List<String> types = SignatureUtils.getParameterSignatures(method.getSignature());
+		if ((types.isEmpty()) || (types.size() > 2)) {
+			return false;
+		}
 
-			if (hasSimilarParms(types)) {
-				return;
-			}
+		String lastParmSig = types.get(types.size() - 1);
+		if (!lastParmSig.startsWith(Values.SIG_ARRAY_PREFIX)
+				|| lastParmSig.startsWith(Values.SIG_ARRAY_OF_ARRAYS_PREFIX)) {
+			return false;
+		}
 
-			if (obj.isStatic() && "main".equals(obj.getName()) && SIG_STRING_ARRAY_TO_VOID.equals(obj.getSignature())) {
-				return;
-			}
+		if (SignatureBuilder.SIG_BYTE_ARRAY.equals(lastParmSig)
+				|| SignatureBuilder.SIG_CHAR_ARRAY.equals(lastParmSig)) {
+			return false;
+		}
 
-			if (!obj.isPrivate() && !obj.isStatic() && isInherited(obj)) {
-				return;
-			}
+		if (hasSimilarParms(types)) {
+			return false;
+		}
 
-			super.visitMethod(obj);
-			bugReporter.reportBug(new BugInstance(this, BugType.UVA_USE_VAR_ARGS.name(), LOW_PRIORITY).addClass(this)
-					.addMethod(this));
+		if (method.isStatic() && "main".equals(method.getName()) && SIG_STRING_ARRAY_TO_VOID.equals(method.getSignature())) {
+			return false;
+		}
 
-		} catch (ClassNotFoundException cnfe) {
-			bugReporter.reportMissingClass(cnfe);
+		if (!method.isPrivate() && !method.isStatic() && isInherited(method)) {
+			return false;
 		}
+		
+		return true;
 	}
 
 	/**