What is a significant characteristic of arrays in contrast to ArrayLists in Java?

A significant characteristic of arrays in contrast to ArrayLists in Java is that they can only hold one type of data. In Java, an array is a fixed-size data structure that can hold a specified number of elements, all of which must be of the same type. This type can be a primitive data type (like int, char, etc.) or a reference type (like a class), but all elements in a single array must be of that designated type.

In contrast, ArrayLists are part of the Java Collections Framework and are more flexible. They allow for dynamic sizing, meaning that you can add or remove elements without needing to know the size beforehand, and they also allow for storing objects of different types if the ArrayList is declared as a certain generic type. Arrays do not offer this level of flexibility and type variance.

This characteristic is crucial because it dictates how arrays are used in Java programming. If you need a collection of heterogeneous data types or require the ability to manipulate the size of the collection easily, ArrayLists would be the appropriate choice.