How does the ArrayList data structure increase in size during program execution?

In Java, ArrayList is implemented based on an array. When the current array is filled and a new element needs to be added, the internal array is increased.

The mechanism of increase:

• When adding an element, it checks if there is enough space in the current array.
• If there is no space, a new array of larger size is created (usually about 1.5 times the current size).
• The contents of the old array are copied into the new one.
• The new element is added to the new array.

This allows ArrayList to grow dynamically while maintaining fast access by index.

Here's an example of how the increase looks:

int newCapacity = oldCapacity + (oldCapacity >> 1); // increase by 50%