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   * fb-contrib - Auxiliary detectors for Java programs
   * Copyright (C) 2005-2013 Dave Brosius
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * Lesser General Public License for more details.
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 package com.mebigfatguy.fbcontrib.detect;
 import java.util.Map;
 import java.util.Set;
 import  org.apache.bcel.classfile.Code;
 import  org.apache.bcel.classfile.Field;
 import  org.apache.bcel.classfile.JavaClass;
 import  org.apache.bcel.classfile.Method;
 import  org.apache.bcel.generic.Type;
 import  edu.umd.cs.findbugs.BugInstance;
 import  edu.umd.cs.findbugs.BugReporter;
 import  edu.umd.cs.findbugs.BytecodeScanningDetector;
 import  edu.umd.cs.findbugs.OpcodeStack;
 import  edu.umd.cs.findbugs.SourceLineAnnotation;

looks for classes that maintain collections or StringBuffer/StringBuilders in static member variables, and that do not appear to provide a way to clear or remove items from these members. Such class fields are likely causes of memory bloat.
 public class PossibleMemoryBloat extends BytecodeScanningDetector
 	private static final Set<StringbloatableSigs = new HashSet<String>();
 	static {
 	private static final Set<StringdecreasingMethods = new HashSet<String>();
 	static {
	private static final Set<StringincreasingMethods = new HashSet<String>();
	static {
	private final BugReporter bugReporter;
	private Map<XField, SourceLineAnnotation> bloatableFields;
	private OpcodeStack stack;
	private String methodName;

constructs a PMB detector given the reporter to report bugs on

bugReporter the sync of bug reports
	public PossibleMemoryBloat(BugReporter bugReporter) {
		this. = bugReporter;

collects static fields that are likely bloatable objects and if found allows the visitor to proceed, at the end report all leftover fields

classContext the class context object of the currently parsed java class
	public void visitClassContext(ClassContext classContext) {
		try {
			 = new HashMap<XField, SourceLineAnnotation>();
			JavaClass cls = classContext.getJavaClass();
			Field[] fields = cls.getFields();
			for (Field f : fields) {
				if (f.isStatic()) {
					String sig = f.getSignature();
					if (.contains(sig)) {
						.put(XFactory.createXField(cls.getClassName(), f.getName(), f.getSignature(), f.isStatic()), null);
			if (.size() > 0) {
				 = new OpcodeStack();
				for (Map.Entry<XField, SourceLineAnnotation> entry : .entrySet()) {
					SourceLineAnnotation sla = entry.getValue();
					if (sla != null) {
						.reportBug(new BugInstance(this"PMB_POSSIBLE_MEMORY_BLOAT", NORMAL_PRIORITY)
finally {
			 = null;

implements the visitor to collect the method name

obj the context object of the currently parsed method
	public void visitMethod(Method obj) {
		 = obj.getName();

implements the visitor to reset the opcode stack

obj the context object of the currently parsed code block
	public void visitCode(Code obj) {
		if ("<clinit>".equals()
		||  "<init>".equals())
		if (.size() > 0)

implements the visitor to look for methods that empty a bloatable field if found, remove these fields from the current list

seen the opcode of the currently parsed instruction
	public void sawOpcode(int seen) {
		try {
			if (.isEmpty())
			if ((seen == INVOKEVIRTUAL)
			||  (seen == INVOKEINTERFACE)) {
				int argCount = Type.getArgumentTypes(sig).length;
				if (.getStackDepth() > argCount) {
					OpcodeStack.Item itm = .getStackItem(argCount);
					XField field = itm.getXField();
					if (field != null) {
						if (.containsKey(field)) {
else if (.contains(mName)) {
								if (.get(field) == null) {
									SourceLineAnnotation sla = SourceLineAnnotation.fromVisitedInstruction(this);
			else if (seen == ARETURN) {
			    if (.getStackDepth() > 0) {
			        OpcodeStack.Item returnItem = .getStackItem(0);
			        XField field = returnItem.getXField();
			        if (field != null) {
		finally {
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