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Java Clone Array: Java Explained

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Gaining a full understanding of Java and its capabilities can be complex, with the language boasting a number of different features and functions. This tutorial will cover one particular technique, known as ‘cloning’, and demonstrate how it can be leveraged in the Java language to create a clone, or copy, of an existing array. We will investigate the benefits and drawbacks of clone arrays, how to create them via different methods, as well as examples of these techniques in action and troubleshooting tips if issues arise.

What is Cloning in Java?

Cloning in Java is a process of creating a duplicate object or array from an existing one. This will create two separate objects or arrays, which are distinct from each other even though their initial values may be the same. The core difference is that the cloned object or array will have its own memory address and will not point to the same contents as the original object or array.

Cloning can be used to produce quick copies of these objects or arrays without needing to rewrite the data they store manually. This is an efficient way of creating multiple copies of the same data with relative ease.

Cloning is also useful when you need to make a deep copy of an object or array. A deep copy will create a new object or array that contains all the same values as the original, but the new object or array will not be linked to the original in any way. This is useful for creating copies of objects or arrays that can be modified without affecting the original.

Benefits and Drawbacks of Cloning in Java

Cloning in Java has a number of useful benefits that make it advantageous in certain situations. It is useful in cases where changes must be made to certain parts of an existing array without modifying the original instance. Cloning lets users maintain the original array while making changes to the clone one and keeps any changes isolated from the original object or array.

The main drawback of clone arrays, however, is that if original object or array changes, modifications will not be reflected in the cloned version. That’s why it’s important to understand the benefits and drawbacks of cloning – and make sure you are aware when changes are made to the original object or array – before you decide to use this feature in Java.

Another potential issue with cloning is that it can be time consuming and resource intensive. Depending on the size of the object or array being cloned, the process can take a significant amount of time and require a large amount of memory. This can be especially problematic if the cloning process needs to be done frequently or on a large scale.

How to Clone an Array in Java

In Java, there are two ways to create a clone of an array. The first is by using the clone method, which creates a shallow copy of an array by copying the elements of the original array into a new one. This method can be used when all elements of the array are immutable objects, such as Strings and Integers. However, if the elements of the array contain references to mutable objects, shallow copies won’t create copies of objects referenced by those elements.

The second way to clone an array in Java is by using the deepCopy() method. This method creates a deep copy of an array, meaning that all elements and objects referenced by those elements are copied in their entirety. This is ideal for arrays which contain both immutable and mutable objects.

When cloning an array, it is important to consider the type of objects that are contained in the array. If the array contains only immutable objects, then the clone method is the best option. However, if the array contains references to mutable objects, then the deepCopy() method should be used to ensure that all objects are copied correctly.

Using the Clone Method to Create a Shallow Copy of an Array

The clone method is used as follows:

// Create an arrayint[] arr = {1, 2, 3}; // Create a clone of the arrayint[] arrClone = arr.clone();

In this example, two separate copies of integer array ‘arr’ were created. The clone method has created a shallow copy of the original array, meaning that elements of the original arr array were copied over into the arrClone array. However, since neither of the elements are mutable objects, this shallow copy works correctly.

Using the DeepCopy Method to Create a Deep Copy of an Array

Using the deepCopy method is essentially identical to using the clone method:

// Create an arrayObject[] arr = {1, new Object(), "a string"};  // Create a deep copy of the array Object[] arrClone = Arrays.deepCopy(arr); 

In this case, a deep copy was created instead of a shallow one due to an element containing references to mutable objects. This means that both ‘arr’ and ‘arrClone’ contain copies of all elements and objects referenced by those elements

Examples of Cloning Arrays in Java

Let’s consider a more concrete example where we have an array ‘origArray’ containing two elements that reference different strings, for instance:

String[] origArray = {"John", "Smith"}; 

Now let’s create a shallow copy with the clone operation:

String[] shallowCopy = origArray.clone(); 

Since neither of the elements are references to mutable objects, this shallow copy works correctly – even if we change element ‘shallowCopy[0]’ to point to another string ‘Bob’:

// Change element 0 on shallowCopy to point to another string shallowCopy[0] = "Bob"; 

The ‘origArray’ still contains ‘John’ and ‘Smith’ as its two elements even after this change is made.

On the other hand, if we create a deep copy instead:

String[] deepCopy = Arrays.deepCopy(origArray); 

And then change element ‘deepCopy[0]’ again:

// Change element 0 on deepCopy to point to another string deepCopy[0] = "Bob"; 

This results in both ‘origArray’ and ‘deepCopy’ containing ‘Bob’ as its first element.

Troubleshooting Common Issues with Cloning Arrays in Java

If you encounter any issues with cloning arrays in Java, one possible issue can arise from not identifying whether you require a shallow or deep cloning operation for your use case. As previously mentioned, shallow clones work for immutable objects, but since elements in the array can be references to immutable or mutable objects this needs to be taken into account.

Additionally, if there are references between elements inside nested arrays then deep copies may be needed to keep both original and cloned arrays consistent with one another. Again, it all depends on whether you have immutable or mutable references in your arrays.

Once these issues have been identified you can create clones with either the clone() or deepCopy() methods which should create copies which are consistent with your expectations.

This tutorial has demonstrated what cloning is in Java, its benefits and drawbacks when compared to other features in the language, as well as how clones can be created using either the clone() or deepCopy() methods. We also looked at examples where these techniques are used followed by a troubleshooting section which explains some of the common issues that can arise when working with clones.

Anand Das

Anand Das

Anand is Co-founder and CTO of Bito. He leads technical strategy and engineering, and is our biggest user! Formerly, Anand was CTO of Eyeota, a data company acquired by Dun & Bradstreet. He is co-founder of PubMatic, where he led the building of an ad exchange system that handles over 1 Trillion bids per day.

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