Make copy of an array

java

array-copying

performance-optimization

multithreading

byNikita Barsukov·Oct 15, 2024

To create a precise duplicate of an array in Java, use the Arrays.copyOf method. Here's how:

import java.util.Arrays;

int[] original = {1, 2, 3};
int[] copy = Arrays.copyOf(original, original.length); //Json, eat your heart out - we're cloning too!

The above code will generate copy, an exact replica of original, with each element accounted for. However, you will find System.arraycopy() and Arrays.copyOfRange() useful for targeted copying or manual control.

Deciding the right method

Choosing the fitting method for array copying is key to write efficient, bug-free code.

src.clone(): A direct, built-in approach to replicate the complete array.
System.arraycopy(): Gives more control over start and end positions in both source and destination arrays; ideal for copying specific sections.
Arrays.copyOfRange(): Comes in handy when you need to copy a range from the source array.

Copying arrays: Handling efficiency and pitfalls

Copying arrays, especially large ones, can impact performance. Besides, there are pitfalls like accidental creation of array references or concurrency issues in multi-thread environments.

Thread safety comes first. Make sure to synchronize, snap, and copy.
Don’t mix up shallow and deep copy. Go deep for objects and stay shallow for the rest.

A closer look at array copying methods

Primitive types: Skip deep copying

int[] intArray = {1, 2, 3};
int[] clonedArray = intArray.clone(); // Power up! Shallow copy deems fit

Objects: Deep copy matters

Object[] objArray = {new Object(), new Object()};
// Watch out! Implement deep copy within Object class or else face deep trouble

For large arrays: Performance

With large data, System.arraycopy() can out-perform clone(). Size matters!

Tackling multi-threading

Synchronize access when running in multi-threaded mode to nip race conditions in the bud.

Advanced copying: Beyond the basics

Need to clone multi-dimensional arrays? Or dealing with immutable contents? Up your game with advanced cloning strategies.

Key reminders

Watch out for these when duplicating arrays:

Modifying a cloned array does not impact the original array- they do not communicate post break-up!
src.clone() makes a shallow copy; deep copy needs you to take the wheel.
Beware of unintentionally creating references instead of true clones.

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