CODEWITHSUNDEEP
java
Muntadher Sallal
Muntadher Sallal

Reputation:

How to get key depending on the value from HashMap

I have a HashMap in Java (named queue) which with Integer as the key and List of messages as a value related to each key. I want to visit all values of List<messages>, and compare each entry with the particular value that I feed it to the function foo(Message m). If the entered value equal the value of HashMap, then get the key of this value and store it in a list. Here is my function:

public static List<Integer> getKey(Message m,MessageList m1) 
    {
        List<Integer> l = new ArrayList<Integer>();


        for(Map.Entry<Integer, List<Message>> entry:m1.queue.entrySet()) {
            if(m.equals(entry.getValue())) {
                l.add(entry.getKey());
            }
        }
        return l;
    }

But this function doesn't work. Is there any wrong?

Upvotes: 0

Views: 112

Answers (1)

Idan Arye
Idan Arye

Reputation: 12633

The value is of type List<Message> but you compare it to a single Message. Use List::contains:

public static List<Integer> getKey(Message m,MessageList m1)
{
    List<Integer> l = new ArrayList<Integer>();


    for(Map.Entry<Integer, List<Message>> entry:m1.queue.entrySet()) {
        if(entry.getValue != null && entry.getValue().contains(m)) {
            l.add(entry.getKey());
        }
    }
    return l;
}

Upvotes: 1

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