Builder模式的真实示例

public class RequestBuilder {
    private String url;
    private String method;
    private Map<String, String> headers;
    private String body;

    public RequestBuilder(String url) {
        this.url = url;
    }

    public RequestBuilder setMethod(String method) {
        this.method = method;
        return this;
    }

    public RequestBuilder setHeaders(Map<String, String> headers) {
        this.headers = headers;
        return this;
    }

    public RequestBuilder setBody(String body) {
        this.body = body;
        return this;
    }

    public Request build() {
        return new Request(url, method, headers, body);
    }
}

Request request = new RequestBuilder("https://example.com")
    .setMethod("POST")
    .setHeaders(Collections.singletonMap("Content-Type", "application/json"))
    .setBody("{ \"message\": \"Hello, world!\" }")
    .build();