CODEWITHSUNDEEP
collectionsvector
Enosh Bansode
Enosh Bansode

Reputation: 1778

How does Vector in Java Collection work

How does Vector in Java Collection work internally so that it can accept any type of Objects

Upvotes: 2

Views: 5251

Answers (4)

Rajesh
Rajesh

Reputation: 1

  1. Vector has initial capacity is 10.
  2. we can define capacityincrement for Vector, if we didn't define capacityIncrement , in that case, Vector grow() will be double.
  3. All methods are synchronized, so thread safety is there.
  4. Returns an enumeration of the components of this vector
  5. Performance is slow compare to ArrayList

Upvotes: 0

JL235
JL235

Reputation: 2645

Internally, Vector just stored objects as type Object. Because all objects inherit from Object, it can store all objects.

Primitive values, such as int and double, however do not inherit from Object, because they are not objects. To cope with them, Java will convert them from primitive values to Objects on the fly, as needed. So the int 5 will be converted to an Integer object holding 5, and the double 4.3 will be converted to a Double object holding 4.3. This is known as auto-boxing.

Java will also do the reverse, convert from Integer to int, for you automatically. This is known as 'un-boxing'.

So that allows it to store any object, but when you code with Vector, you can be more specific. For example Vector or Vector. This restriction on what you can store inside the Vector, is achieved using 'generics', which allows you to pass in a type as a parameter to the class. In those examples that parameter is String and Integer.

Generics however is only enforced at compile time; at runtime, Vector will just continue to use Object internally.

What this means is that when your application is running, there is no difference between Vector and Vector. They are exactly the same, and in fact there is only Vector (no Vector or Vector really exists). The difference between them is entirely at compile time, before the application runs, where with Vector, it will only compile if you only store String objects within it.

Upvotes: 3

Priyank Doshi
Priyank Doshi

Reputation: 13151

Vector works same as List. The only different it methods of Vector are synchronised while for List, Synchronization is a responsibility of programmer.

Upvotes: -1

Paul Sasik
Paul Sasik

Reputation: 81429

It works because of Polymorphism, which is a key idea in object oriented languages such as Java and is one of the four pillars of object oriented programming.

Vector is type a collection of Objects and since all classes in Java inherit from Object, Vector can accept any type of object.

Upvotes: 1

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