如何在flink中只获取大型数据集的最后一个元素？

import org.apache.flink.api.common.functions.ReduceFunction;
import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.api.windowing.assigners.TumblingProcessingTimeWindows;
import org.apache.flink.streaming.api.windowing.time.Time;

public class LastElementExample {

    public static void main(String[] args) throws Exception {
        // 创建执行环境
        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

        // 读取数据集，假设数据集为DataStream<String>类型
        DataStream<String> input = env.fromElements("element1", "element2", "element3", ...);

        // 将数据集划分为窗口，窗口大小为1，即每个窗口只包含一个元素
        DataStream<String> windowedStream = input
                .windowAll(TumblingProcessingTimeWindows.of(Time.milliseconds(1)));

        // 使用ReduceFunction将窗口中的元素合并为一个元素，保留最后一个元素
        DataStream<String> result = windowedStream.reduce(new ReduceFunction<String>() {
            @Override
            public String reduce(String value1, String value2) throws Exception {
                return value2; // 保留最后一个元素
            }
        });

        // 输出最后一个元素
        result.print();

        // 执行程序
        env.execute("Last Element Example");
    }
}