Builder Pattern With Fluent Interface

RestUrl.java

/**
 * @author Nadeem Mohammad
 */
public class RestUrl {

    private String url;

    private RestUrl(String url) {
        this.url = url;
    }

    public String get() {
        return url;
    }

    public static BaseUrl builder() {
        return new Builder();
    }

    public static class Builder implements BaseUrl, RequestUri, UrlParam, Build {
        private static final String SLASH = "/";
        public static final String BRACE_OPEN = "{";
        public static final String BRACE_CLOSE = "}";

        private StringBuilder buffer;

        public Builder () {
            this.buffer = new StringBuilder();
        }

        @Override
        public Builder baseUrl(String baseUrl) {
            if (baseUrl.endsWith("/")) {
                baseUrl = baseUrl.substring(0, baseUrl.length() - 1);
            }
            buffer.append(baseUrl);
            return this;
        }

        @Override
        public Builder requestUri(String requestUri) {
            if (!requestUri.startsWith(SLASH)) {
                requestUri = SLASH + requestUri;
            }
            buffer.append(requestUri);
            return this;
        }

        @Override
        public UrlParam urlParam(String urlParam) {
            buffer.append(urlParam);
            return this;
        }

        @Override
        public UrlParam urlPlaceHolderParam(String urlParam) {
            buffer.append(BRACE_OPEN).append(urlParam).append(BRACE_CLOSE);
            return this;
        }

        @Override
        public RestUrl build() {
            return new RestUrl(buffer.toString());
        }
    }

    interface BaseUrl {
        RequestUri baseUrl(String baseUrl);
    }

    interface RequestUri {
        UrlParam requestUri(String requestUri);
    }

    interface UrlParam {
        UrlParam urlParam(String urlParam);
        UrlParam urlPlaceHolderParam(String urlParam);
        RestUrl build();
    }

    interface Build {
        RestUrl build();
    }
}