[英]How to retrive Value by using key from Hashmap<String, String>?
这是我的代码:
public static HashMap<String, ArrayList<String>> CountryMap = new HashMap<String, ArrayList<String>>();
ArrayList<String> stateInd = new ArrayList<String>();
ArrayList<String> stateUSA = new ArrayList<String>();
stateInd.add("GJ");
stateInd.add("MP");
stateUSA.add("NJ");
stateUSA.add("NY");
CountryMap.put("India",stateInd);
CountryMap.put("USA",stateUSA);
for(int i=0;i<CountryMap.size();i++){
for (Entry<String, ArrayList<String>> entry : CountryMap.entrySet()) {
if (entry.getKey().equals("India") {
ArrayList<String> result = new ArrayList<String>();
# how to add Value of CountryMap with "India" as a Key to result ArrayList??
}
}
}
我想将哈希值添加到另一个以“印度”为键的ArrayList中的值吗?
我试过了..
result.add(CountryMap.get("India"));
但这没有用。 它添加所有值。
解决方案1:
result.addAll(CountryMap.get("India"));
解决方案2:
result.add(CountryMap.get("India").toString());
请尝试看看所有引发的功能和异常。 回复是否有效
public class NewClass4{
public static HashMap<String, ArrayList<String>> CountryMap = new HashMap<String, ArrayList<String>>();
public static void main(String[] args)
{
ArrayList<String> stateInd = new ArrayList<String>();
ArrayList<String> stateUSA = new ArrayList<String>();
stateInd.add("GJ");
stateInd.add("MP");
stateUSA.add("NJ");
stateUSA.add("NY");
CountryMap.put("India",stateInd);
CountryMap.put("USA",stateUSA);
ArrayList<String> result = new ArrayList<String>();
result=CountryMap.get("India");
if(result!=null){
// means CountryMap contain key "India"
}
}
}
嗨,我知道这已经快一个月了,但我忍不住想了一下。 如果我正确回答您的问题,解决方案将非常简单。
public static void main(String[] args) {
HashMap<String, ArrayList<String>> CountryMap = new HashMap<String, ArrayList<String>>();
ArrayList<String> stateInd = new ArrayList<String>();
ArrayList<String> stateUSA = new ArrayList<String>();
ArrayList<String> result = new ArrayList<String>();
stateInd.add("GJ");
stateInd.add("MP");
stateUSA.add("NJ");
stateUSA.add("NY");
CountryMap.put("India",stateInd);
CountryMap.put("USA",stateUSA);
for (String key: CountryMap.keySet()){
if (key.equals("India")){
result.add(key);
}
}
for (String country: result){
System.out.print("\n"+country+" ");
}
}
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