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Kevin Meredith
Kevin Meredith

Reputation: 41939

Create Map in Java

I'd like to create a map that contains entries consisting of (int, Point2D)

How can I do this in Java?

I tried the following unsuccessfully.

HashMap hm = new HashMap();

hm.put(1, new Point2D.Double(50, 50));

Upvotes: 130

Views: 470555

Answers (6)

dreamcrash
dreamcrash

Reputation: 51613

With the newer Java versions (i.e., Java 9 and forwards) you can use :

Map.of(1, new Point2D.Double(50, 50), 2, new Point2D.Double(100, 50), ...)

generically:

Map.of(Key1, Value1, Key2, Value2, KeyN, ValueN)

Bear in mind however that Map.of only works for at most 10 entries, if you have more than 10 entries that you can use :

Map.ofEntries(entry(1, new Point2D.Double(50, 50)), entry(2,  new Point2D.Double(100, 50)), ...);

Upvotes: 22

KJTester
KJTester

Reputation: 407

I use such kind of a Map population thanks to Java 9. In my honest opinion, this approach provides more readability to the code.

  public static void main(String[] args) {
    Map<Integer, Point2D.Double> map = Map.of(
        1, new Point2D.Double(1, 1),
        2, new Point2D.Double(2, 2),
        3, new Point2D.Double(3, 3),
        4, new Point2D.Double(4, 4));
    map.entrySet().forEach(System.out::println);
  }

Upvotes: 7

Durgpal Singh
Durgpal Singh

Reputation: 11983

Java 9 

public static void main(String[] args) {
    Map<Integer,String> map = Map.ofEntries(entry(1,"A"), entry(2,"B"), entry(3,"C"));
}

Upvotes: 32

webdizz
webdizz

Reputation: 846

There is even a better way to create a Map along with initialization:

Map<String, String> rightHereMap = new HashMap<String, String>()
{
    {
        put("key1", "value1");
        put("key2", "value2");
    }
};

For more options take a look here How can I initialise a static Map?

Upvotes: 37

Achrome
Achrome

Reputation: 7821

Map<Integer, Point2D> hm = new HashMap<Integer, Point2D>();

Upvotes: 11

hd1
hd1

Reputation: 34677

Map <Integer, Point2D.Double> hm = new HashMap<Integer, Point2D>();
hm.put(1, new Point2D.Double(50, 50));

Upvotes: 157

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