[英]How to retrive Value by using key from Hashmap<String, String>?
這是我的代碼:
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??
}
}
}
我想將哈希值添加到另一個以“印度”為鍵的ArrayList中的值嗎?
我試過了..
result.add(CountryMap.get("India"));
但這沒有用。 它添加所有值。
解決方案1:
result.addAll(CountryMap.get("India"));
解決方案2:
result.add(CountryMap.get("India").toString());
請嘗試看看所有引發的功能和異常。 回復是否有效
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,我知道這已經快一個月了,但我忍不住想了一下。 如果我正確回答您的問題,解決方案將非常簡單。
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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