Program: 149413
Project: 149413
Buggy source:
private static int collectSlavesToRemove(List<ElasticBoxSlave> slavesToRemove) throws IOException {
  ElasticBoxCloud cloud=ElasticBoxCloud.getInstance();
  Client ebClient=new Client(cloud.getEndpointUrl(),cloud.getUsername(),cloud.getPassword());
  int numOfInstances=0;
  for (  Node node : Jenkins.getInstance().getNodes()) {
    if (node instanceof ElasticBoxSlave && !isSlaveInQueue((ElasticBoxSlave)node,incomingQueue)) {
      final ElasticBoxSlave slave=(ElasticBoxSlave)node;
      if (slave.isSingleUse() && slave.getComputer() != null) {
        boolean remove=true;
        for (        hudson.model.Queue.BuildableItem item : Jenkins.getInstance().getQueue().getBuildableItems(slave.getComputer())) {
          if (!item.getFuture().isCancelled()) {
            remove=false;
            break;
          }
          ;
        }
        if (remove) {
          slavesToRemove.add(slave);
          break;
        }
      }
      if (slave.getInstanceUrl() != null) {
        try {
          JSONObject instance=ebClient.getInstance(slave.getInstanceId());
          String state=instance.getString("String_Node_Str");
          if (Client.InstanceState.DONE.equals(state) && Client.TERMINATE_OPERATIONS.contains(instance.getString("String_Node_Str"))) {
            addToTerminatedQueue(slave);
          }
 else           if (Client.InstanceState.UNAVAILABLE.equals(state) || (slave.canTerminate() && !isSlaveInQueue(slave,submittedQueue))) {
            Logger.getLogger(ElasticBoxSlaveHandler.class.getName()).log(Level.INFO,MessageFormat.format("String_Node_Str",slave.getInstanceUrl()));
            slavesToRemove.add(slave);
          }
 else {
            numOfInstances++;
          }
        }
 catch (        ClientException ex) {
          if (ex.getStatusCode() == HttpStatus.SC_NOT_FOUND) {
            slavesToRemove.add(slave);
          }
        }
      }
 else       if (!slave.isInUse()) {
        slavesToRemove.add(slave);
      }
    }
  }
  return numOfInstances;
}

Fixed version (ground truth):
private static int collectSlavesToRemove(List<ElasticBoxSlave> slavesToRemove) throws IOException {
  ElasticBoxCloud cloud=ElasticBoxCloud.getInstance();
  Client ebClient=new Client(cloud.getEndpointUrl(),cloud.getUsername(),cloud.getPassword());
  int numOfInstances=0;
  for (  Node node : Jenkins.getInstance().getNodes()) {
    if (node instanceof ElasticBoxSlave && !isSlaveInQueue((ElasticBoxSlave)node,incomingQueue)) {
      final ElasticBoxSlave slave=(ElasticBoxSlave)node;
      if (slave.isSingleUse() && slave.canTerminate() && slave.getComputer() != null) {
        boolean remove=true;
        for (        hudson.model.Queue.BuildableItem item : Jenkins.getInstance().getQueue().getBuildableItems(slave.getComputer())) {
          if (!item.getFuture().isCancelled()) {
            remove=false;
            break;
          }
          ;
        }
        if (remove) {
          slavesToRemove.add(slave);
          break;
        }
      }
      if (slave.getInstanceUrl() != null) {
        try {
          JSONObject instance=ebClient.getInstance(slave.getInstanceId());
          String state=instance.getString("String_Node_Str");
          if (Client.InstanceState.DONE.equals(state) && Client.TERMINATE_OPERATIONS.contains(instance.getString("String_Node_Str"))) {
            addToTerminatedQueue(slave);
          }
 else           if (Client.InstanceState.UNAVAILABLE.equals(state) || (slave.canTerminate() && !isSlaveInQueue(slave,submittedQueue))) {
            Logger.getLogger(ElasticBoxSlaveHandler.class.getName()).log(Level.INFO,MessageFormat.format("String_Node_Str",slave.getInstanceUrl()));
            slavesToRemove.add(slave);
          }
 else {
            numOfInstances++;
          }
        }
 catch (        ClientException ex) {
          if (ex.getStatusCode() == HttpStatus.SC_NOT_FOUND) {
            slavesToRemove.add(slave);
          }
        }
      }
 else       if (!slave.isInUse()) {
        slavesToRemove.add(slave);
      }
    }
  }
  return numOfInstances;
}