java - 打印出一个数组列表，并选择 1 的索引？

Question

possibleRoutes类型为HashSet<ArrayList<Integer>> 。 possibleRoutes 中的每个数组均列出包含按行驶顺序相互连接的地铁站或火车站的 ID。

for( ArrayList<Integer> route : possibleRoutes) {

        ArrayList<Double> routesDistances = new ArrayList<Double>(); // list of the total distances of the routes

        double distance = 0;

        for (int i=1; i < route.size()-1; i++){
            double x = Math.abs(stationLocations.get(route.get(i)).getX() - stationLocations.get(route.get(i-1)).getX());
            double y = Math.abs(stationLocations.get(route.get(i)).getY() - stationLocations.get(route.get(i-1)).getY());
            double d = Math.sqrt(Math.pow(x, 2) + Math.pow(y, 2));

            distance += d;;
        }

        routesDistances.add(distance);

        System.out.print(routesDistances);

    }

这是到目前为止的输出:

[2163.9082950470897][3494.746239392733][2099.5269818921306][2075.3141294013]

我想将列表打印为数组列表，我可以从列表中选择一个索引，例如 routesDistances.get(0)至于第一个索引。如何使列表成为 ArrayList<Double> 类型并返回为:

[2163.9082950470897, 3494.746239392733, 2099.5269818921306, 2075.3141294013]

Answer 1

直接放

ArrayList<Double> routesDistances = new ArrayList<Double>();

before

for( ArrayList<Integer> route : possibleRoutes)

循环后，您的routesDistances将如下所示:[2163.9082950470897, 3494.746239392733, 2099.5269818921306, 2075.3141294013]

然后一个循环中的输出就这样写:

for(Double d:routesDistances){
    System.out.println(d);
}