Question

我必须保存一个Collection并访问它（从一个循环中），但我无法找到一种方法...对我的程序有任何建议..我刚刚开始学习Java。感谢

public class Main {

public static void main(String[] args) {
    // my hashmap
    Map<String, List<String>> test_01 = new HashMap<>();
    Scanner scanner = new Scanner(System.in);
    String answer;
    List<String> name = new ArrayList<>();
    List<String> time = new ArrayList<>();
    String lake_Name, lake_time;
    do {
        System.out.println("Enter the name of the lake : ");
        lake_Name = scanner.nextLine();
        name.add(lake_Name);

        System.out.println("Enter the name of the running time : ");
        lake_time = scanner.nextLine();
        time.add(lake_time);
        //I'm doing this just in case my user does not enter a number

        System.out.println("Do you want add another lake  :  \"Y\" for Yes  OR another key to see the statistic  the problem ");
        answer = scanner.nextLine();
    } while (answer.equalsIgnoreCase("Y"));
    //We can continue here to do more stuff
    for (int i = 0; i < name.size(); i++) {
        putObjects(test_01, name.get(i), time.get(i));
    }

    /*Collection<String> x = test_01.get("x");
    System.out.println(x);*/
    // to get unique elements
    Set<String> treesetList = new TreeSet<String>(name);
    // to iterate again
    List<String> list = new ArrayList<> (treesetList);


    for (String s : treesetList){
         Collection<String> uno = test_01.get(s);
         System.out.println(uno);
    }


}

private static void putObjects (Map<String, List<String>> a, String key, String value) {
    List<String> myClassList = a.get(key);
    if(myClassList == null) {
        myClassList = new ArrayList<>();
        a.put(key, myClassList);
    }
    myClassList.add(value);
}

}

我的问题在这里

for (String s : treesetList){
        Collection<String> uno = test_01.get(s);                 
        System.out.println(uno);
    }

因为我必须在＆＃34; test_01＆＃34;中访问不同的湖名称及其集合。从地图...我不知道如何保存到具有不同名称（或创建它们）的不同数组，以便我可以检查它的时间....我将把集合转换为＆＃34; double＆＃34;后来...

Answer 1

创建集合，然后使用add。

List<String> aList = new ArrayList<String>();    
for (String s : treesetList){
     aList.add(test_01.get(s));
}

for (String str : aList){
  System.out.println(str);
}

将集合保存在循环中

1 个答案: