What is the default size of Vector, Arraylist, Hashtable, Hashmap, Hashset in Java?

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  • Sep 22nd, 2007

As we know vector, ArrayList, etc are all growable so I think the size is not specific but depends upon the heap area of JVM. If I am not right please tell.

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  • Nov 24th, 2007

Vector has a default size of 10

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  • Dec 4th, 2007

A vector has its default capacity which is 10 elements, here size is different from capacity, after 10 element if we enter one element the capacity of vector changes to 20 were as size is 11 only, for example if you have entered 21 elements in a vector, then if you print v.size it results 21 but v.capacity it results 30 If you have any further queries pls let me know

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  • Nov 21st, 2011

vector size every time get double.

For example: Initially capacity is 10, when when you will put 11 th value in this it will give you size 20, when you will add 21 value its size would be 40 ans after that 80 ans so on,
but in case of array list its increment 50 % of the existing.

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  • Nov 21st, 2011

Instead of 30 it would give 40.

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  • Aug 9th, 2012

ArrayList , Vector default size is 10. vector increment is 10 and array list is 10/2

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  • Mar 3rd, 2014


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Saurabh Ranjan

  • Jan 1st, 2015

after 10th element if we insert 11th element in ArrayList it will increase by capacity=(currentCapacity*3/2)+1

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  • Oct 10th, 2015

Current Capacity+3/2,10*3/2=16

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Java 6:
Vector = 10
Arraylist = 10
Hashtable = 11
Hashmap = 16
Hashset = 16
Java 7:
Vector = 10
Arraylist = 0. Size will change to 10 once we add the element in the list
Hashtable = 11
Hashmap = 0. Size will change to 16 once we add the element in the map
Hashset = 0. Size will change to 16 once we add the element in the set

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  • Jan 23rd, 2017

Vector class increment by 10 & ArrayList increment by [capacity=capacity*3/2]

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Vivek Ranjan Singh

  • Apr 24th, 2017

Mitesh the calculation part of your solution is not right, kindly check it. Also you are using wrong formula to solve the growable size of the ArrayList.

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Rishiraj Verma

  • Jul 20th, 2017


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Azaz Patel

  • Aug 20th, 2017

new capacity=(currentCapacity+3/2)+1

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