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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  org.apache.bcel.Constants;
 import  org.apache.bcel.classfile.Code;
 import  org.apache.bcel.classfile.Method;
 import  edu.umd.cs.findbugs.BugInstance;
 import  edu.umd.cs.findbugs.BugReporter;
 import  edu.umd.cs.findbugs.BytecodeScanningDetector;
 import  edu.umd.cs.findbugs.OpcodeStack;

looks for methods that pass single character string constants as parameters to methods that alternatively have an overridden method that accepts a character instead. It is easier for the method to handle a single character than a String.
 public class UseCharacterParameterizedMethod extends BytecodeScanningDetector 
 	private static Map<StringIntegercharacterMethods = new HashMap<StringInteger>();
 	static {
 		//characterMethods.put("java/lang/StringBuffer:append:(Ljava/lang/String;)Ljava/lang/StringBuffer;", Integer.valueOf(0));
 		//characterMethods.put("java/lang/StringBuilder:append:(Ljava/lang/String;)Ljava/lang/StringBuilder;", Integer.valueOf(0));
 		.put("java/lang/String:indexOf:(Ljava/lang/String;)I", Integer.valueOf(0));
 		.put("java/lang/String:indexOf:(Ljava/lang/String;I)I", Integer.valueOf(1));
 		.put("java/lang/String:lastIndexOf:(Ljava/lang/String;)I", Integer.valueOf(0));
 		.put("java/lang/String:lastIndexOf:(Ljava/lang/String;I)I", Integer.valueOf(1));
 		//characterMethods.put("java/lang/String:startsWith:(Ljava/lang/String;)Z", Integer.valueOf(0));
 		.put("java/io/PrintStream:print:(Ljava/lang/String;)V", Integer.valueOf(0));
 		.put("java/io/PrintStream:println:(Ljava/lang/String;)V", Integer.valueOf(0));
 		.put("java/io/StringWriter:write:(Ljava/lang/String;)V", Integer.valueOf(0));
 	private BugReporter bugReporter;
 	private OpcodeStack stack;

constructs a UCPM detector given the reporter to report bugs on

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

overrides the visitor to create and clear the opcode stack

context the context object for the currently parsed class
 	public void visitClassContext(final ClassContext context) {
 		try {
 			 = new OpcodeStack();
 			if (context.getJavaClass().getMajor() >= Constants.MAJOR_1_5) {
 				.put("java/lang/StringBuffer:append:(Ljava/lang/String;)Ljava/lang/StringBuffer;", Integer.valueOf(0));
 		} finally {
 			 = null;

looks for methods that contain a LDC opcode

obj the context object of the current method
if the class uses LDC instructions
 	private boolean prescreen(Method obj) {
 		BitSet bytecodeSet = getClassContext().getBytecodeSet(obj);
 		return (bytecodeSet != null) && ((bytecodeSet.get(Constants.LDC) || (bytecodeSet.get(Constants.LDC_W))));

implement the visitor prescreen the method, and reset the stack

obj the context object for the currently parsed method
	public void visitCode(Code obj) {
		if (prescreen(getMethod())) {

implements the visitor to look for method calls that pass a constant string as a parameter when the string is only one character long, and there is an alternate method passing a character.
	public void sawOpcode(int seen) {
		try {
			if ((seen == INVOKEVIRTUAL) || (seen == INVOKEINTERFACE)) {
				Integer parmPos =.get(key);
				if (parmPos != null) {
					int stackPos = parmPos.intValue();
					if (.getStackDepth() > stackPos) {
						OpcodeStack.Item itm = .getStackItem(stackPos);
						String con = (String)itm.getConstant();
						if ((con != null) && (con.length() == 1)) {
finally {
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