public MessageRequest addEndpointsEntry(String key, EndpointSendConfiguration value) {
        if (null == this.endpoints) {
            this.endpoints = new java.util.HashMap<String, EndpointSendConfiguration>();
        }
        if (this.endpoints.containsKey(key))
            throw new IllegalArgumentException("Duplicated keys (" + key.toString() + ") are provided.");
        this.endpoints.put(key, value);
        return this;
    }
Add a single Endpoints entry

@see MessageRequest#withEndpoints
@returns a reference to this object so that method calls can be chained together.
aws-java-sdk-pinpoint/src/main/java/com/amazonaws/services/pinpoint/model/MessageRequest.java