Question

让我说我有这样的事情：

LinkedHashMap <String, ArrayList<String>> h 
keyOne has
stringOne 
stringTwo 
stringThree

keyTwo has
stringOne

如何计算关联键的ArrayList的大小？所以对于keyOne，它应该给我3个。

Answer 1

你有没有尝试过：

ArrayList<String> tmp = h.get("keyOne");
if ( tmp != null ) {
    return tmp.size();
} else {
    return 0;
}

Answer 2

你可以写h.get(key).size()

Answer 3

int count = h.get("keyOne").size();

应该这样做。

Answer 4

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.Set;

public class Test {
    public static void main(String[] args) {
        LinkedHashMap<String, ArrayList<String>> h = new LinkedHashMap<String, ArrayList<String>>();
        ArrayList<String> al1 = new ArrayList<String>();
        al1.add("Value11");
        al1.add("Value12");
        al1.add("Value13");
        ArrayList<String> al2 = new ArrayList<String>();
        al2.add("Value21");
        h.put("key1", al1);
        h.put("key2", null);
        Set<String> set = h.keySet();
        for (String key : set) {
            ArrayList<String> al = h.get(key);
            if (al != null)
                System.out.println (key + " : " + al.size());
            else
                System.out.println (key + " is empty ");
        } 
    }
}

输出：

key1 : 3
key2 is empty

计算LinkedHashMap中的键<string，arraylist <string =“”>＆gt; </string，>

4 个答案: