Chapter 8: Problem 26

What is the difference between an ArrayList object’s size and its capacity?

Short Answer

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Answer: The size of an ArrayList refers to the number of elements currently stored in it during a program's execution, whereas the capacity is the amount of storage space available within the ArrayList, which can hold the elements. Capacity is the maximum number of elements that the ArrayList can hold before it needs to be resized. As elements are added, the size increases, and if necessary, the capacity grows dynamically to accommodate new elements.

Step by step solution

Understanding an ArrayList

An ArrayList in Java is a resizable-array implementation of the List interface. It uses a dynamic array to store elements and can grow or shrink in size as elements are added or removed.

Defining size and capacity

The size of an ArrayList refers to the number of elements currently stored in the ArrayList during a program's execution. The capacity, on the other hand, is the amount of storage space available within the ArrayList, which can hold the elements. In simple terms, capacity is the maximum number of elements that the ArrayList can hold before it needs to be resized.

Example of size and capacity

Let's assume an ArrayList is created as follows: ArrayList myList = new ArrayList<>(4); This creates an ArrayList named myList, with an initial capacity of 4. At this point, the ArrayList is empty, meaning its size is 0. The capacity, however, is the amount of storage space available for elements and in this case, it is 4.

Adding elements to the ArrayList

Now, if we were to add elements to myList: myList.add(1); myList.add(2); The size of myList would increase from 0 to 2, since two elements have been added. However, the capacity of myList remains unchanged at 4 since there is still space for more elements.

Explaining growth of capacity in ArrayList

When the number of elements in an ArrayList exceeds its capacity, the capacity is increased. ArrayLists automatically grow by a factor of 1.5 of their current capacity when they run out of room. This growth factor helps avoid frequent resizing and makes ArrayList an efficient data structure for dynamic storage needs. In summary, the size of an ArrayList represents the number of elements currently stored in it, while the capacity is the amount of storage space available inside the ArrayList, which can hold the elements. The capacity grows dynamically as needed, to accommodate new elements.

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What is the difference between an ArrayList object’s size and its capacity?

Short Answer

Step by step solution

Understanding an ArrayList

Defining size and capacity

Example of size and capacity

Adding elements to the ArrayList

Explaining growth of capacity in ArrayList

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