I think you should write equals() like this:
```
    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        DbTableDescr other = (DbTableDescr) obj;
        if (mDbName == null) {
            if (other.mDbName != null)
                return false;
        } else if (!mDbName.equals(other.mDbName))
            return false;
        if (mTableName == null) {
            if (other.mTableName != null)
                return false;
        } else if (!mTableName.equals(other.mTableName))
            return false;
        if (mTableType != other.mTableType)
            return false;
        return true;
    }
```
If you use Eclipse, you can use "Source > Generate hashCode() and equals()" :)