How to get String key from HashMap?

Question

I have a HashMap with String key and String value. I want to get an item from list, I tried to give key and wanted to get value but it gives an error. The following example how can I get "both" value with give the key "blazer"?

 HashMap<String,String> upper = new HashMap<>();
 upper.put("shoulder","both");
 upper.put("blazer","both");

 if(upper.get(upper.get("blazer"))) {} //gives an "incompatible types" error. 
 //Error: Required: boolean Found: java.lang.String

Answer 1

They way you have it there upper.get(upper.get("blazer")); would just return null.

You're passing in upper.get("blazer") (which would return "both") to your outer upper.get . Since you have no "both" key stored in your map, it returns null.

Should be:

upper.get("blazer");

Answer 2

Understand that upper.get(key) will not return a boolean value. You have defined your HashMap as follows:

HashMap<String,String> upper = new HashMap<>();

This means that both the key and value will be of type String . Thus, providing a valid key the the get() method will return a String :

String myValue = upper.get("blazer");

If you wish to check if a key is available before you attempt to read the value you can use the method containsKey() with will return a boolean value indicating whether the HashMap contains an entry with the given key :

if(upper.containsKey("blazer")){
    String myValue = upper.get("blazer");
    Log.e(TAG, "Yes blazer is available : " + myValue);
} 
else{
    Log.e(TAG, "No blazer is available!");
}

You can also iterate through the available key s like this:

Set<String> set = map.keySet();
for(String s : set){
    Log.e(TAG, "Map key = " + s + " value = " + map.get(s));
}