Question

用户输入2 sting，存储在变量a和b中。现在程序中存在很多ArrayList，我们要检查是否存在一个存在于变量a中的名称的ArrayList。那我怎么能这样做呢？

public static void root(String a,String b)
{
    ArrayList chicago=new ArrayList();
    chicago.add("newyork");
    chicago.add("new jersy");
    chicago.add("dallas");

    ArrayList buffalo=new ArrayList();
    buffalo.add("arlington");
    buffalo.add("california");
    buffalo.add("dallas");

    ArrayList newyork=new ArrayList();
    newyork.add("chicago");
    newyork.add("paris");
    newyork.add("nigara");

    ArrayList stations=new ArrayList();
    stations.add(chicago);
    stations.add(buffalo);
    stations.add(newyork);

    if(stations.contains(a))
    {


    }

}

Answer 1

这应该对你有用（虽然不是最佳解决方案）：

import java.util.ArrayList;
import java.util.Iterator;

public class Test2 {
    public Test2() {
        // TODO Auto-generated constructor stub
    }

    public static void main(String[] args) {
        // Test a String.
        String test = "newyork";
        String test2 = "dallas";
        root(test, test2);
    }

    public static void root(String a,String b)
    {
        ArrayList<String> chicago=new ArrayList();
        chicago.add("newyork");
        chicago.add("new jersy");
        chicago.add("dallas");

        ArrayList<String> buffalo=new ArrayList();
        buffalo.add("arlington");
        buffalo.add("california");
        buffalo.add("dallas");

        ArrayList<String> newyork=new ArrayList();
        newyork.add("chicago");
        newyork.add("paris");
        newyork.add("nigara");

        ArrayList<ArrayList> stations=new ArrayList();
        stations.add(chicago);
        stations.add(buffalo);
        stations.add(newyork);

        // Go through each ArrayList.
        Iterator<ArrayList> arrStations = stations.iterator();
        while(arrStations.hasNext()){
            ArrayList<String> tmp = arrStations.next();
            if(tmp.contains(a)){
                // a is in the ArrayList.
                System.out.println("String '" + a + "', is in");
            }
        }
    }
}

Answer 2

看起来你有一个嵌套的ArrayList。如果你想查找a是否存在，你将需要遍历嵌套数组列表

public static void root(String a,String b)
{
  ArrayList chicago=new ArrayList();
  chicago.add("newyork");
  chicago.add("new jersy");
  chicago.add("dallas");

  ArrayList buffalo=new ArrayList();
  buffalo.add("arlington");
  buffalo.add("california");
  buffalo.add("dallas");

  ArrayList newyork=new ArrayList();
  newyork.add("chicago");
  newyork.add("paris");
  newyork.add("nigara");

  ArrayList stations=new ArrayList();
  stations.add(chicago);
  stations.add(buffalo);
  stations.add(newyork);


 for(Object o : stations) {
    //cast the object back to an arrayList
    ArrayList l = (ArrayList) o;

    if(l.contains(a))
    {

        System.out.println("Found");
        break;
    }else {
        System.out.println("Not found");
    }
}

Answer 3

使用类似HashMap<String, List<String>>的内容。 HashMap中的键可能是您在此处使用的字符串。

Map<String,List<String>> map = new HashMap<>();

ArrayList<String> chicago=new ArrayList<>();
chicago.add("newyork");
chicago.add("new jersy");
chicago.add("dallas");
map.put("chicago", chicago);

等等。

然后你要检查的条件是

if (map.containsKey(a) && map.get(a).contains(b)) {
    ...
}

String对象到ArrayList对象

3 个答案: