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How do I know whether to use an array or an arraylist?

stackoverflow.com › questions › 24860857 › how-do-i-know-whether-to-use-an-array-or-an-arraylist

Some more differences:

First and Major difference between Array and ArrayList in Java is that Array is a fixed length data structure while ArrayList is a variable length Collection class. You can not change length of Array once created in Java but ArrayList re-size itself when gets full depending upon capacity and load factor. Since ArrayList is internally backed by Array in Java, any resize operation in ArrayList will slow down performance as it involves creating new Array and copying content from old array to new array.
Another difference between Array and ArrayList in Java is that you can not use Generics along with Array, as Array instance knows about what kind of type it can hold and throws ArrayStoreException, if you try to store type which is not convertible into type of Array. ArrayList allows you to use Generics to ensure type-safety.
One more major difference between ArrayList and Array is that, you can not store primitives in ArrayList, it can only contain Objects. While Array can contain both primitives and Objects in Java. Though Autoboxing of Java 5 may give you an impression of storing primitives in ArrayList, it actually automatically converts primitives to Object.
Java provides add() method to insert element into ArrayList and you can simply use assignment operator to store element into Array e.g. In order to store Object to specified position.
One more difference on Array vs ArrayList is that you can create instance of ArrayList without specifying size, Java will create Array List with default size but its mandatory to provide size of Array while creating either directly or indirectly by initializing Array while creating it. By the way you can also initialize ArrayList while creating it.

Answer from Braj on Stack Overflow

reddit.com › r/learnprogramming › java: is arraylist better than arrays?

r/learnprogramming on Reddit: Java: Is Arraylist better than Arrays?

June 23, 2024 -

I've been programming in Java for 10 months now (as a subject in school) and i was always curious whats the biggest difference between Areays and Arraylist. I know that if i had an Arraylist named 'list' and i wrote System.out.print(list) it will print all the things that the list contains. Something that Arrays can't do that easily. But whats the actually biggest difference?

Top answer

1 of 12

The biggest difference is that you can add to and remove from a list, whereas arrays have a fixed size.

2 of 12

u/sepp2k pointed the biggest difference. The other one is array notation. Because ArrayLists are much more frequently used than arrays, but arrays use standard array syntax, working with ArrayLists are slightly more annoying. // Arrays int x = arr[2]; // Look up a value arr[2] = 10; // Set a value // ArrayLists int x = list.get(2); // instead of list[2] list.set(2, 10); // Instead of arr[2] = 10 It's the set method that's awkward to use, but it does raise the point of how arr[2] has different meanings depending on whether it's on the right side of an assignment statement or the left side. On the right side, arr[2] refers to the value stored in arr[2]. This is sometimes called the r-value. On the left side of the assignment operator, arr[2] refers to the memory location (i.e., where in memory is arr[2] stored), not to its content. This is called an l-value. Most programmers don't even realize this distinction until you point it out to them. With ArrayLists, however, you use get (which is an r-value) and put (which is an l-value). The following does NOT work with ArrayLists list.get(2) = 10; // Won't compile

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geeksforgeeks.org › java › array-vs-arraylist-in-java

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June 5, 2026 - An array has a fixed size, while ArrayList is dynamic and part of the Java Collections Framework, offering more built-in methods for easy data manipulation.

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What's the different between ArrayList and List?

ArrayList is a class that implements ... You can reference an ArrayList object with a List reference eg: List aList = new ArrayList(). ... I understood the difference between Array vs.... More on teamtreehouse.com

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what is the diffrence between list and ArrayList?

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r/learnjava

December 17, 2022

Why use array over arraylist?

ArrayLists have overhead associated with them especially when it comes to using primitive values. Because ArrayLists are a Collection class, they can only store references objects. For that reason, primitive values are wrapped by equivalent classes representing those primitive (for example, Integer wraps int). Those classes add overhead in terms of memory usage and performance. You can add regular ints using an add method but the compiler just turns those into objects in what's known as autoboxing/unboxing hence the performance issues. Doesn't really matter though if you're not trying to implement a highly-performant system. More on reddit.com

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February 5, 2016

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