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Client library for working with the NATS messaging system.

There is a newer version: 2.20.5

// Copyright 2022 The NATS Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at:
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package io.nats.client.api;

/**
 * Use the Watcher interface to watch for updates
 */
public interface Watcher {

    /**
     * Called when an object has been updated
     *
     * @param t The watched object
     */
    void watch(T t);

    /**
     * Called once if there is no data when the watch is created
     * or if there is data, the first time the watch exhausts all existing data.
     */
    void endOfData();
}