// snippet-sourcedescription:[ListCollections.java demonstrates how to list the available Amazon Rekognition collections.]
// snippet-service:[Amazon Rekognition]
// snippet-keyword:[Java]
// snippet-keyword:[Amazon Rekognition]
// snippet-keyword:[Code Sample]
// snippet-sourcetype:[full-example]
// snippet-sourcedate:[6-10-2020]
// snippet-sourceauthor:[scmacdon - AWS]

/**
 * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * This file is licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License. A copy of
 * the License is located at
 *
 * http://aws.amazon.com/apache2.0/
 *
 * This file 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 com.example.rekognition;

// snippet-start:[rekognition.java2.list_collections.import]
import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.rekognition.RekognitionClient;
import software.amazon.awssdk.services.rekognition.model.ListCollectionsRequest;
import software.amazon.awssdk.services.rekognition.model.ListCollectionsResponse;
import software.amazon.awssdk.services.rekognition.model.RekognitionException;
import java.util.List;
// snippet-end:[rekognition.java2.list_collections.import]

public class ListCollections {

    public static void main(String[] args) {

        Region region = Region.US_EAST_2;
        RekognitionClient rekClient = RekognitionClient.builder()
                .region(region)
                .build();

        System.out.println("Listing collections");
        listAllCollections(rekClient);
    }

    // snippet-start:[rekognition.java2.list_collections.main]
    public static void listAllCollections(RekognitionClient rekClient) {

        try {

            // Create a ListCollectionsRequest object
            ListCollectionsRequest listCollectionsRequest = ListCollectionsRequest.builder()
                    .maxResults(10)
                    .build();

            // Invoke the listCollections method
            ListCollectionsResponse response = rekClient.listCollections(listCollectionsRequest);

            // Display the results
            List<String> collectionIds = response.collectionIds();
            for (String resultId : collectionIds) {
                System.out.println(resultId);
            }

        } catch (RekognitionException e) {
            System.out.println(e.getMessage());
            System.exit(1);
        }
        // snippet-end:[rekognition.java2.list_collections.main]
    }
}

Create ListCollections.java