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ArrayList in Java vs. Vector in Java — What's the Difference?

By Tayyaba Rehman & Fiza Rafique — Published on January 31, 2024
ArrayList in Java is resizable, non-synchronized, and allows random access, while Vector in Java is synchronized, thread-safe, and slower due to thread safety.
ArrayList in Java vs. Vector in Java — What's the Difference?

Difference Between ArrayList in Java and Vector in Java


Key Differences

In Java, an ArrayList is a resizable array implementation of the List interface, offering dynamic array resizing. Vector, also a part of the Java Collection framework, is similar to ArrayList but synchronizes each individual operation. While ArrayList provides fast iteration and fast random access, Vector's synchronized methods ensure thread safety at the expense of performance.
ArrayList in Java is not synchronized, meaning it's not thread-safe and should be used in a single-threaded environment. In contrast, Vector in Java is synchronized, making it thread-safe but less efficient in single-threaded scenarios due to the overhead of synchronization. This synchronization in Vector can lead to performance issues in high-concurrency environments, whereas ArrayList is generally faster under most circumstances.
The capacity increment behavior of ArrayList and Vector is another point of differentiation. When an ArrayList needs to grow, it increases its size by half of its current size. Vector, however, allows the user to specify the increment value for its capacity; if not specified, it doubles the current capacity each time it needs to grow. This flexibility in Vector can be advantageous when working with large data sets and needing to manage memory usage carefully.
ArrayList is generally preferred in newer Java applications due to its performance advantages over Vector. Vector, being a legacy class introduced in Java 1.0, is still used in applications for its thread-safe properties, especially in older Java programs where thread safety is a concern. Modern alternatives to Vector, like the thread-safe collections from the java.util.concurrent package, offer better options for concurrent applications, making ArrayList and these modern alternatives more suitable for current Java development.
In terms of API, both ArrayList and Vector provide similar functionalities, as they both implement the List interface. However, Vector includes a few additional legacy methods that are not part of the Collection framework. These methods, such as 'addElement', 'elementAt', and 'removeElement', provide a bridge to older, pre-Java Collection API code, whereas ArrayList strictly adheres to the Collection framework's methods and conventions. This distinction is crucial for maintaining compatibility with older Java codebases.

Comparison Chart



Thread Safety

Not thread-safe by default


Faster for non-threaded operations
Slower due to synchronization

Capacity Increment

Increases size by 50% automatically
Allows specifying capacity increment

Recommended Use

Preferred in non-threaded scenarios
Used when thread safety is required

Compare with Definitions

ArrayList in Java

ArrayList in Java dynamically resizes, allowing more elements than its initial size.
We used an ArrayList to store the list of attendees dynamically.

Vector in Java

Allows setting the increment rate of its capacity.
We optimized memory usage by controlling the capacity increment of our Vector.

ArrayList in Java

Allows fast random access to elements.
Retrieving the fifth element from our ArrayList was instantaneous.

Vector in Java

Part of Java's collection framework, though less preferred than ArrayList.
Despite its performance cost, we used Vector for its built-in synchronization.

ArrayList in Java

Not synchronized, making it faster but not thread-safe.
For our single-threaded application, we chose ArrayList for its speed.

Vector in Java

Vector in Java is a thread-safe dynamic array.
For our multi-threaded application, we used a Vector to ensure data integrity.

ArrayList in Java

It is part of Java's collection framework, providing rich functionalities.
We leveraged the Collections.sort method on our ArrayList of prices.

Vector in Java

Older collection class in Java, still used for thread-safe operations.
We chose Vector over ArrayList due to its legacy in our old Java system.

ArrayList in Java

Its ability to resize itself makes it more flexible than a static array.
The ArrayList adapted its size as we added more customer records.

Vector in Java

Its methods are synchronized, making it suitable for concurrent access.
Vector's thread-safe nature was crucial for our concurrent user sessions.

Common Curiosities

What is an ArrayList in Java?

A resizable array, part of Java's collection framework, offering fast access but not synchronized.

Are ArrayList operations thread-safe?

No, ArrayList is not synchronized and not inherently thread-safe.

Why would one use Vector over ArrayList?

Vector is used when thread safety is a priority, despite its performance cost.

How does ArrayList handle size increments?

ArrayList automatically increases its size by 50% when needed.

Are there alternatives to Vector for thread-safe operations?

Yes, other collections like CopyOnWriteArrayList offer thread safety with different performance characteristics.

What is a Vector in Java?

A synchronized, resizable array, suitable for thread-safe operations but slower than ArrayList.

Can we specify the initial capacity of an ArrayList?

Yes, ArrayList allows setting an initial capacity.

Does Vector allow control over capacity increments?

Yes, Vector allows specifying the rate at which its capacity should increase.

How does the performance of ArrayList and Vector compare?

ArrayList is generally faster due to lack of synchronization overhead.

Can ArrayList and Vector be used interchangeably?

While they have similar functionalities, their use depends on the need for thread safety.

Is Vector considered a legacy class?

Yes, Vector is older and often considered legacy, but still used for its thread safety.

Is it possible to manually synchronize an ArrayList?

Yes, ArrayList can be synchronized externally using Collections.synchronizedList.

Can we iterate over ArrayList and Vector in the same way?

Yes, both support standard iteration methods like for-each loops.

Is ArrayList part of Java SE 8?

Yes, ArrayList is part of Java Standard Edition 8 and beyond.

What is the main drawback of using Vector?

The main drawback is its performance penalty due to synchronized methods.

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Author Spotlight

Written by
Tayyaba Rehman
Tayyaba Rehman is a distinguished writer, currently serving as a primary contributor to As a researcher in semantics and etymology, Tayyaba's passion for the complexity of languages and their distinctions has found a perfect home on the platform. Tayyaba delves into the intricacies of language, distinguishing between commonly confused words and phrases, thereby providing clarity for readers worldwide.
Co-written by
Fiza Rafique
Fiza Rafique is a skilled content writer at, where she meticulously refines and enhances written pieces. Drawing from her vast editorial expertise, Fiza ensures clarity, accuracy, and precision in every article. Passionate about language, she continually seeks to elevate the quality of content for readers worldwide.

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