code: @Override
      public void doExecute() {
          if (!getEditor().isReadOnly()) {
              deleted = getEditor().delete().charAt(0);
              if (Character.isLetter(deleted) && Character.isLowerCase(deleted)) {
                  getEditor().put(deleted.toString().toUpperCase());
                  getEditor().moveLeft(1);
              } else {
                  if (Character.isLetter(deleted) && Character.isUpperCase(deleted)) {
                      getEditor().put(deleted.toString().toLowerCase());
                      getEditor().moveLeft(1);
                  }
              }
          }
      }
docs: Executes the {@link org.jledit.command.Command}.