Program: 59
Project: 59
Buggy source:
public String getInterfaceLanguagePreference(XWikiContext context){
  String language="String_Node_Str", requestLanguage="String_Node_Str", userPreferenceLanguage="String_Node_Str", navigatorLanguage="String_Node_Str", cookieLanguage="String_Node_Str", contextLanguage="String_Node_Str";
  boolean setCookie=false;
  if (!context.getWiki().isMultiLingual(context)) {
    language=Util.normalizeLanguage(context.getWiki().getXWikiPreference("String_Node_Str","String_Node_Str",context));
    context.setInterfaceLanguage(language);
    return language;
  }
  try {
    requestLanguage=Util.normalizeLanguage(context.getRequest().getParameter("String_Node_Str"));
  }
 catch (  Exception ex) {
  }
  contextLanguage=context.getInterfaceLanguage();
  try {
    String user=context.getUser();
    XWikiDocument userdoc=null;
    userdoc=getDocument(user,context);
    if (userdoc != null) {
      userPreferenceLanguage=userdoc.getStringValue("String_Node_Str","String_Node_Str");
    }
  }
 catch (  XWikiException e) {
  }
  if (context.getRequest() != null) {
    String accept=context.getRequest().getHeader("String_Node_Str");
    if ((accept != null) && (!accept.equals("String_Node_Str"))) {
      String[] alist=StringUtils.split(accept,"String_Node_Str");
      if ((alist != null) && !(alist.length == 0)) {
        context.setLanguage(alist[0]);
        navigatorLanguage=alist[0];
      }
    }
  }
  try {
    cookieLanguage=Util.normalizeLanguage(getUserPreferenceFromCookie("String_Node_Str",context));
  }
 catch (  Exception e) {
  }
  if ((requestLanguage != null) && (!requestLanguage.equals("String_Node_Str"))) {
    if (requestLanguage.equals("String_Node_Str")) {
      setCookie=true;
    }
 else {
      language=requestLanguage;
      context.setLanguage(language);
      Cookie cookie=new Cookie("String_Node_Str",language);
      cookie.setMaxAge(60 * 60 * 24* 365* 10);
      cookie.setPath("String_Node_Str");
      context.getResponse().addCookie(cookie);
      return language;
    }
  }
  if (contextLanguage != null && contextLanguage != "String_Node_Str") {
    language=contextLanguage;
  }
 else   if (cookieLanguage != null && cookieLanguage != "String_Node_Str") {
    language=cookieLanguage;
  }
 else   if (userPreferenceLanguage != null && userPreferenceLanguage != "String_Node_Str") {
    language=userPreferenceLanguage;
  }
 else   if (navigatorLanguage != null && navigatorLanguage != "String_Node_Str") {
    language=navigatorLanguage;
  }
  context.setLanguage(language);
  if (setCookie) {
    Cookie cookie=new Cookie("String_Node_Str",language);
    cookie.setMaxAge(60 * 60 * 24* 365* 10);
    cookie.setPath("String_Node_Str");
    context.getResponse().addCookie(cookie);
  }
  return language;
}

Fixed version (ground truth):
public String getInterfaceLanguagePreference(XWikiContext context){
  String language="String_Node_Str", requestLanguage="String_Node_Str", userPreferenceLanguage="String_Node_Str", navigatorLanguage="String_Node_Str", cookieLanguage="String_Node_Str", contextLanguage="String_Node_Str";
  boolean setCookie=false;
  if (!context.getWiki().isMultiLingual(context)) {
    language=Util.normalizeLanguage(context.getWiki().getXWikiPreference("String_Node_Str","String_Node_Str",context));
    context.setInterfaceLanguage(language);
    return language;
  }
  try {
    requestLanguage=Util.normalizeLanguage(context.getRequest().getParameter("String_Node_Str"));
  }
 catch (  Exception ex) {
  }
  contextLanguage=context.getInterfaceLanguage();
  try {
    String user=context.getUser();
    XWikiDocument userdoc=null;
    userdoc=getDocument(user,context);
    if (userdoc != null) {
      userPreferenceLanguage=userdoc.getStringValue("String_Node_Str","String_Node_Str");
    }
  }
 catch (  XWikiException e) {
  }
  if (context.getRequest() != null) {
    String accept=context.getRequest().getHeader("String_Node_Str");
    if ((accept != null) && (!accept.equals("String_Node_Str"))) {
      String[] alist=StringUtils.split(accept,"String_Node_Str");
      if ((alist != null) && !(alist.length == 0)) {
        context.setLanguage(alist[0]);
        navigatorLanguage=alist[0];
      }
    }
  }
  try {
    cookieLanguage=Util.normalizeLanguage(getUserPreferenceFromCookie("String_Node_Str",context));
  }
 catch (  Exception e) {
  }
  if ((requestLanguage != null) && (!requestLanguage.equals("String_Node_Str"))) {
    if (requestLanguage.equals("String_Node_Str")) {
      setCookie=true;
    }
 else {
      language=requestLanguage;
      context.setLanguage(language);
      Cookie cookie=new Cookie("String_Node_Str",language);
      cookie.setMaxAge(60 * 60 * 24* 365* 10);
      cookie.setPath("String_Node_Str");
      context.getResponse().addCookie(cookie);
      return language;
    }
  }
  if (contextLanguage != null && contextLanguage != "String_Node_Str") {
    language=contextLanguage;
  }
 else   if (StringUtils.isNotEmpty(cookieLanguage)) {
    language=cookieLanguage;
  }
 else   if (StringUtils.isNotEmpty(userPreferenceLanguage)) {
    language=userPreferenceLanguage;
  }
 else   if (StringUtils.isNotEmpty(navigatorLanguage)) {
    language=navigatorLanguage;
  }
  context.setLanguage(language);
  if (setCookie) {
    Cookie cookie=new Cookie("String_Node_Str",language);
    cookie.setMaxAge(60 * 60 * 24* 365* 10);
    cookie.setPath("String_Node_Str");
    context.getResponse().addCookie(cookie);
  }
  return language;
}