```
public class Filter
extends Object
```
The `Filter` trait defines behavior for indicating chain activity of interest pertaining to channels. This is useful in order to have a [`Watch`] implementation convey to a chain source which transactions to be notified of. Notification may take the form of pre-filtering blocks or, in the case of [BIP 157]/[BIP 158], only fetching a block if the compact filter matches. If receiving full blocks from a chain source, any further filtering is unnecessary. After an output has been registered, subsequent block retrievals from the chain source must not exclude any transactions matching the new criteria nor any in-block descendants of such transactions. Note that use as part of a [`Watch`] implementation involves reentrancy. Therefore, the `Filter` should not block on I/O. Implementations should instead queue the newly monitored data to be processed later. Then, in order to block until the data has been processed, any [`Watch`] invocation that has called the `Filter` must return [`InProgress`]. [`InProgress`]: ChannelMonitorUpdateStatus::InProgress [BIP 157]: https://github.com/bitcoin/bips/blob/master/bip-0157.mediawiki [BIP 158]: https://github.com/bitcoin/bips/blob/master/bip-0158.mediawiki

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`protected void`	`finalize()`
`static Filter`	`new_impl(Filter.FilterInterface arg)`
`void`	`register_output(WatchedOutput output)`	Registers interest in spends of a transaction output.
`void`	`register_tx(byte[] txid, byte[] script_pubkey)`	Registers interest in a transaction with `txid` and having an output with `script_pubkey` as a spending condition.

Class Filter