Program: 137571
Project: 137571
Buggy source:
public IStatus validate(Object[] selection){
  IStatus status=new Status(IStatus.OK,CorePlugin.PLUGIN_ID,StringUtils.EMPTY);
  if (selection != null && selection.length > 2) {
    status=new Status(IStatus.ERROR,CorePlugin.PLUGIN_ID,DefaultMessagesImpl.getString("String_Node_Str"));
  }
  for (  Object selectObject : selection) {
    if (selectObject instanceof IFile) {
      IFile file=(IFile)selectObject;
      if (FactoriesUtil.DQRULE.equals(file.getFileExtension())) {
        MatchRuleDefinition matchRule=DQRuleResourceFileHelper.getInstance().findMatchRule(file);
        if ((matchRule.getBlockKeys() == null || matchRule.getBlockKeys().size() < 1) && (matchRule.getMatchRules() == null || matchRule.getMatchRules().size() < 1)) {
          status=new Status(IStatus.ERROR,CorePlugin.PLUGIN_ID,DefaultMessagesImpl.getString("String_Node_Str"));
          return status;
        }
        String warningMsg=StringUtils.EMPTY;
        if (T_SWOOSH_ALGORITHM.equals(matchRule.getRecordLinkageAlgorithm())) {
          warningMsg=DefaultMessagesImpl.getString("String_Node_Str");
        }
        boolean needColumnWarning=false;
        if (dialogType != MATCHGROUP_TYPE) {
          for (          BlockKeyDefinition bkd : matchRule.getBlockKeys()) {
            for (            String col : inputColumnNames) {
              if (!col.equalsIgnoreCase(bkd.getColumn()) && !col.equalsIgnoreCase(bkd.getName())) {
                needColumnWarning=true;
                break;
              }
            }
            if (needColumnWarning) {
              break;
            }
          }
        }
        if (dialogType != GENKEY_TYPE) {
          for (          MatchRule rule : matchRule.getMatchRules()) {
            EList<MatchKeyDefinition> matchKeys=rule.getMatchKeys();
            for (            MatchKeyDefinition mkd : matchKeys) {
              for (              String col : inputColumnNames) {
                if (!col.equalsIgnoreCase(mkd.getColumn()) && !col.equalsIgnoreCase(mkd.getName())) {
                  needColumnWarning=true;
                  break;
                }
              }
              if (needColumnWarning) {
                break;
              }
            }
            if (needColumnWarning) {
              break;
            }
          }
        }
        if (needColumnWarning) {
          warningMsg=DefaultMessagesImpl.getString("String_Node_Str");
        }
        if (!StringUtils.EMPTY.equals(warningMsg)) {
          status=new Status(IStatus.WARNING,CorePlugin.PLUGIN_ID,warningMsg);
        }
      }
    }
  }
  return status;
}

Fixed version (ground truth):
public IStatus validate(Object[] selection){
  IStatus status=new Status(IStatus.OK,CorePlugin.PLUGIN_ID,StringUtils.EMPTY);
  if (selection != null && selection.length > 2) {
    status=new Status(IStatus.ERROR,CorePlugin.PLUGIN_ID,DefaultMessagesImpl.getString("String_Node_Str"));
  }
  for (  Object selectObject : selection) {
    if (selectObject instanceof IFile) {
      IFile file=(IFile)selectObject;
      if (FactoriesUtil.DQRULE.equals(file.getFileExtension())) {
        MatchRuleDefinition matchRule=DQRuleResourceFileHelper.getInstance().findMatchRule(file);
        if ((matchRule.getBlockKeys() == null || matchRule.getBlockKeys().size() < 1) && (matchRule.getMatchRules() == null || matchRule.getMatchRules().size() < 1)) {
          status=new Status(IStatus.ERROR,CorePlugin.PLUGIN_ID,DefaultMessagesImpl.getString("String_Node_Str"));
          return status;
        }
        String warningMsg=StringUtils.EMPTY;
        if (T_SWOOSH_ALGORITHM.equals(matchRule.getRecordLinkageAlgorithm())) {
          warningMsg=DefaultMessagesImpl.getString("String_Node_Str");
        }
        boolean needColumnWarning=false;
        if (dialogType != MATCHGROUP_TYPE) {
          for (          BlockKeyDefinition bkd : matchRule.getBlockKeys()) {
            boolean hasColumnMatch=false;
            for (            String col : inputColumnNames) {
              if (col.equalsIgnoreCase(bkd.getColumn()) || col.equalsIgnoreCase(bkd.getName())) {
                hasColumnMatch=true;
                break;
              }
            }
            if (!hasColumnMatch) {
              needColumnWarning=true;
              break;
            }
          }
        }
        if (dialogType != GENKEY_TYPE) {
          for (          MatchRule rule : matchRule.getMatchRules()) {
            EList<MatchKeyDefinition> matchKeys=rule.getMatchKeys();
            for (            MatchKeyDefinition mkd : matchKeys) {
              boolean hasColumnMatch=false;
              for (              String col : inputColumnNames) {
                if (col.equalsIgnoreCase(mkd.getColumn()) || col.equalsIgnoreCase(mkd.getName())) {
                  hasColumnMatch=true;
                  break;
                }
              }
              if (!hasColumnMatch) {
                needColumnWarning=true;
                break;
              }
            }
            if (needColumnWarning) {
              break;
            }
          }
        }
        if (needColumnWarning) {
          warningMsg=DefaultMessagesImpl.getString("String_Node_Str");
        }
        if (!StringUtils.EMPTY.equals(warningMsg)) {
          status=new Status(IStatus.WARNING,CorePlugin.PLUGIN_ID,warningMsg);
        }
      }
    }
  }
  return status;
}