Java Stream实战：从字符串数值列表中高效提取最大值

list.stream()
    .mapToInt(Integer::parseInt)
    .max()
    .orElse(-1);

import java.util.ArrayList;
import java.util.List;
import java.util.OptionalInt; // 引入OptionalInt，虽然在直接使用orElse时可能不需要显式导入
import java.util.stream.Collectors; // 一般用于Stream操作，此处未直接使用

// 假设 AllForecast, NextDays, WeeklyForecast 等类已定义，
// 且 WeeklyForecast 构造函数接受一个 int 类型的 rain 参数。

// WeeklyForecast 示例模型
class WeeklyForecast {
    private String date;
    private String tempMax;
    private String tempMin;
    private int rain; // 注意：这里是 int 类型

    public WeeklyForecast(String date, String tempMax, String tempMin, int rain) {
        this.date = date;
        this.tempMax = tempMax;
        this.tempMin = tempMin;
        this.rain = rain;
    }
    // Getters ...
}

// NextDays 示例模型 (简化)
class NextDays {
    private NextDate data;
    private List<String> rain; // 注意：这里是 List<String> 类型
    private NextTemperature temperature;

    public NextDate getData() { return data; }
    public List<String> getRain() { return rain; }
    public NextTemperature getTemperature() { return temperature; }
    // Setters ...
}

// 辅助类 (简化)
class NextDate { public String getData() { return "2023-10-26"; } }
class NextTemperature { public String getMaximumTemperature() { return "25"; } public String getMinimumTemperature() { return "15"; } }
class AllForecast { public List<NextDays> getNextDays() { 
    // 模拟数据
    NextDays day1 = new NextDays(); day1.rain = List.of("100", "95"); day1.data = new NextDate(); day1.temperature = new NextTemperature();
    NextDays day2 = new NextDays(); day2.rain = List.of("80", "75", "90"); day2.data = new NextDate(); day2.temperature = new NextTemperature();
    NextDays day3 = new NextDays(); day3.rain = new ArrayList<>(); // 空列表
    return List.of(day1, day2, day3); 
} }
class Templates { public static AllForecast restTemplate(Object restTemplate) { return new AllForecast(); } }


public class ForecastConverter {

    // 假设 restTemplate 实例已通过依赖注入或其他方式提供
    private Object restTemplate; // 替换为实际的 RestTemplate 类型

    public ForecastConverter(Object restTemplate) {
        this.restTemplate = restTemplate;
    }

    public List<WeeklyForecast> convert(){
        AllForecast allForecast = Templates.restTemplate(restTemplate);
        List<NextDays> nextDaysList = allForecast.getNextDays();
        List<WeeklyForecast> result = new ArrayList<>();

        for (int i = 0; i < nextDaysList.size(); i++){
            NextDays currentDayData = nextDaysList.get(i);

            // 核心逻辑：从 List<String> 中提取最大降雨概率
            int maxRainProbability = currentDayData.getRain().stream()
                                                    .mapToInt(Integer::parseInt) // 将String转换为int
                                                    .max()                       // 获取OptionalInt最大值
                                                    .orElse(-1);                 // 如果列表为空，则返回-1作为默认值

            // 构建 WeeklyForecast 对象
            WeeklyForecast weekly = new WeeklyForecast(
              currentDayData.getData().getData(),
              currentDayData.getTemperature().getMaximumTemperature(),
              currentDayData.getTemperature().getMinimumTemperature(),
              maxRainProbability // 将计算出的最大值赋给 WeeklyForecast
            );

            result.add(i, weekly); // 或者 result.add(weekly); 如果不需要指定索引
        }

        return result;   
    }

    public static void main(String[] args) {
        ForecastConverter converter = new ForecastConverter(null); // 实际应用中传入 RestTemplate 实例
        List<WeeklyForecast> forecasts = converter.convert();
        for (WeeklyForecast wf : forecasts) {
            System.out.println("Date: " + wf.date + ", Max Temp: " + wf.tempMax + ", Min Temp: " + wf.tempMin + ", Max Rain Prob: " + wf.rain);
        }
    }
}