方法映射((<no type> cfg) -&gt; {}) 对于 List 类型是未定义的<capture#1-of ? extends Config>

Question

I am afraid this is the matter of simple lambda map function. But I have no idea how. Below is my java codes,

public SparkConf createSparkConf(String appName, Config config) {
    SparkConf sparkConf = new SparkConf().setMaster(config.getString("system.master")).setAppName(appName);

    config.getConfigList("spark").map(cfg -> {
        String name = "spark." + cfg.getString("name");
        String value = cfg.getString("value");
        sparkConf.set(name, value);
    });

    if(config.hasPath("app")) {
        config.getConfigList("app").map(cfg -> {
            String name = "spark." + cfg.getString("name");
            String value = cfg.getString("value");
            sparkConf.set(name, value);
        });
    }

    return sparkConf;
}

But the map function throws the following exception.

The method map((<no type> cfg) -> {}) is undefined for the type List<capture#1-of ? extends Config>

config.getConfigList("app") line returns List<Config> , but I have no idea why map function throws such errors. Any idea?

Answer 1

You're looking for the forEach method, since you're not collecting the results of the map operation. Also you can call list.stream().map(...) to reach it.