CODEWITHSUNDEEP
javalistconstructortreemap
aLogic
aLogic

Reputation: 125

TreeMap constructor of List values

I have a Class1 with private attribute TreeMap<Long, List<Class2>> tree; and others, I want to write a constructor Class1(Class1 copyOfClass1). Should I create the List values of the TreeMap explicitly (e.g., in a loop), or using this.tree=new TreeMap(copyOfClass1.tree) does that?

Upvotes: 0

Views: 396

Answers (1)

Xavier Delamotte
Xavier Delamotte

Reputation: 3599

If you use this.tree=new TreeMap(copyOfClass1.tree) it will be equivalent as 

this.tree=new TreeMap();
this.tree.putAll(copyOfClass1.tree)

However, it will not make a copy of the list that are stored in the map. The keys will be pointing to the same lists.

If you dont want this behavior I would suggest to iterate over the entries and to make a copy of the lists.

    this.tree = new TreeMap<Long, List<Class2>>();
    for (Entry<Long, List<Class2>> entry : copyOfClass1.tree.entrySet()) {
        this.tree.put(entry.getKey(), new ArrayList<Class2>(entry.getValue()));
    }

Upvotes: 1

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