Program: 19727
Project: 19727
Buggy source:
/** 
 * This method enables agents to form groups. It uses a heuristic based on mutual trust and the socio-economic beliefs. The agent can either try the heuristic with another free agent or with an existing group. The priority is to find an existing group to join. If that fails then we check compatibility between two free agents.
 * @param none
 * @return The group ID that this agent has chosen to join. If null no group is chosen. If leaveGroup is returned the agent requested to leave the group
 */
@Override protected String chooseGroup(){
  String chosenGroup="String_Node_Str";
  System.out.println("String_Node_Str");
  for (  String groupID : getConn().availableGroups()) {
    int size=getConn().getGroupById(groupID).getMemberList().size();
    System.out.println(getConn().getGroupById(groupID).getName() + "String_Node_Str" + size);
    for (    String a : getConn().getGroupById(groupID).getMemberList()) {
      System.out.println("String_Node_Str" + getConn().getAgentById(a).getName());
    }
  }
  System.out.println("String_Node_Str");
  System.out.println();
  System.out.println();
  if (this.getDataModel().getGroupId() != null) {
    if (groupFounders.containsKey(this.getId())) {
      groupFounders.remove(this.getId());
    }
    if (invitationHolders.contains(this.getId())) {
      invitationHolders.remove(this.getId());
      invitationToGroup=null;
    }
    if (membersToKickOut.contains(this.getId())) {
      membersToKickOut.remove(this.getId());
      return leaveGroup;
    }
    if (SatisfiedInGroup()) {
      return null;
    }
 else {
      checkToEvict();
      return leaveGroup;
    }
  }
 else   if (this.invitationToGroup != null && invitationHolders.contains(this.getId())) {
    return invitationToGroup;
  }
 else   if (!getConn().availableGroups().isEmpty()) {
    chosenGroup=agentGroupGrouping();
  }
  if (chosenGroup.equals("String_Node_Str")) {
    chosenGroup=freeAgentsGrouping();
  }
  return chosenGroup;
}

Fixed version (ground truth):
/** 
 * This method enables agents to form groups. It uses a heuristic based on mutual trust and the socio-economic beliefs. The agent can either try the heuristic with another free agent or with an existing group. The priority is to find an existing group to join. If that fails then we check compatibility between two free agents.
 * @param none
 * @return The group ID that this agent has chosen to join. If null no group is chosen. If leaveGroup is returned the agent requested to leave the group
 */
@Override protected String chooseGroup(){
  String chosenGroup="String_Node_Str";
  if (this.getDataModel().getGroupId() != null) {
    if (groupFounders.containsKey(this.getId())) {
      groupFounders.remove(this.getId());
    }
    if (invitationHolders.contains(this.getId())) {
      invitationHolders.remove(this.getId());
      invitationToGroup=null;
    }
    if (membersToKickOut.contains(this.getId())) {
      membersToKickOut.remove(this.getId());
      return leaveGroup;
    }
    if (SatisfiedInGroup()) {
      return null;
    }
 else {
      checkToEvict();
      return leaveGroup;
    }
  }
 else   if (this.invitationToGroup != null && invitationHolders.contains(this.getId())) {
    return invitationToGroup;
  }
 else   if (!getConn().availableGroups().isEmpty()) {
    chosenGroup=agentGroupGrouping();
  }
  if (chosenGroup.equals("String_Node_Str")) {
    chosenGroup=freeAgentsGrouping();
  }
  return chosenGroup;
}