code: protected void assertObjectNotNull(String variableName, Object value) {
          if (variableName == null) {
              String msg = "The value should not be null: variableName=null value=" + value;
              throw new IllegalArgumentException(msg);
          }
          if (value == null) {
              String msg = "The value should not be null: variableName=" + variableName;
              throw new IllegalArgumentException(msg);
          }
      }
docs: ==============