public FieldValue plus(FieldValue o) {
    if (type != o.type) {
      throw new IllegalArgumentException("invalid type");
    }

    switch (type) {
      case STRING:
        return new FieldValue(((String) value).concat((String) o.value), type);

      case INTEGER:
        return new FieldValue(((Integer) value) + ((Integer) o.value), type);

      case LONG:
        return new FieldValue(((Long) value) + ((Long) o.value), type);

      case FLOAT:
      case PERCENT:
        return new FieldValue(((Float) value) + ((Float) o.value), type);

      case SIZE:
        Size size = (Size) value;
        Size oSize = (Size) o.value;
        Size.Unit unit = size.getUnit();
        return new FieldValue(new Size(size.get(unit) + oSize.get(unit), unit), type);

      default:
        throw new AssertionError();
    }
  }
Represents a value of a field. The type of a value is defined by {@link FieldValue}.
hbase-hbtop/src/main/java/org/apache/hadoop/hbase/hbtop/field/FieldValue.java