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

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 keys like this:

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

Answer 2

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");