initialize non-static hashmap with standard keys in java

Question

Am looking for an efficient way to initialize a HashMap given that it's keys remain the same for any object created of the class it belongs to.

My current implementation initializes the HashMap everytime a new class object is created.

Thanks!

If I understand this correctly, you have a class Foo with a field Bar that is a HashMap of some type and for all Foo, the HashMap Bar contains the same keys? Do the values change? — WPrecht
– WPrecht, Commented Nov 12, 2013 at 19:42

PaulProgrammer · Accepted Answer · 2013-11-12 19:35:41Z

1

You can create a template Map, and use .clone() to generate new instances. You could also create a custom Map implementation that uses a copy-on-write policy to refer to a template "parent" Map.

answered Nov 12, 2013 at 19:35

PaulProgrammer

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4 Comments

leba-lev Over a year ago

something along the lines of shallowCopy = (Map<String, Object>) ((HashMap<String, Object>) data).clone();, where data is a template static map?

PaulProgrammer Over a year ago

Yep... That's one way which might work for you. TMTOWTDI. (There's More Than One Way To Do It).

leba-lev Over a year ago

it'd sure be nice to see another way...:)

PaulProgrammer Over a year ago

Create your own HashMap extension facade that takes a "parent" Map as a constructor. In all the access methods, check to see if the key is known to the instance first. If there, return that; if not, return the parent's instance value.

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