method admin() is undefined for the type RestHighLevelClient

Question

I'm using Ingest Attachment Processor Plugin on elasticsearch. I need to set attachment optionswith Java API. How can I do that?

I am creating index and setting pipeline like below:

RestHighLevelClient restHighLevelClient = null;
    File file = new File(filePath);
    try {
        FileInputStream fileInputStreamReader = new FileInputStream(file);
        byte[] bytes = new byte[(int) file.length()];
        fileInputStreamReader.read(bytes);
        encodedfile = new String(Base64.getEncoder().encodeToString(bytes));
        //System.out.println(encodedfile);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }

    try {
        if (restHighLevelClient != null) {
            restHighLevelClient.close();
        }
    } catch (final Exception e) {
        System.out.println("Error closing ElasticSearch client: ");
    }

    try {
        restHighLevelClient = new RestHighLevelClient(RestClient.builder(new HttpHost("localhost", 9200, "http"),
                new HttpHost("localhost", 9201, "http")));
    } catch (Exception e) {
        System.out.println(e.getMessage());
    }

    try (XContentBuilder jsonBuilder = XContentFactory.jsonBuilder()) {
        BytesReference pipelineSource = jsonBuilder.startObject()
                .field("description", "Extract attachment information")
                .startArray("processors")
                  .startObject()
                    .startObject("foreach")
                      .field("field", "my_field")
                      .startObject("processor")
                        .startObject("attachment")
                          .field("field", "_ingest._value.my_base64_field")
                          .field("target_field", "_ingest._value.my_base64_field")
                          .field("ignore_missing", true)
                          .field("indexed_chars", -1)
                        .endObject()
                      .endObject()
                    .endObject()
                  .endObject()
                .endArray()
                .endObject().bytes();
        restHighLevelClient.admin().cluster().preparePutPipeline("my_pipeline",
                pipelineSource, XContentType.JSON).get(); //throwing error on this line. 
    }

Am facing an issue in using .admin() method.

`.admin()` is undefined for the type RestHighLevelClient

Which method i can use instead of .admin() method.