Guava Ints.toArray() method in Java
This post will discuss about Guava Ints.toArray() method to convert a collection of numbers to an int array in Java.
1. Overview of Ints.toArray() method
The Guava Ints.toArray() method takes a Collection<? extends Number> as an argument and returns an int array containing each value of the collection, converted to an int value in the manner of Number.intValue(). The method handles null values by throwing a NullPointerException. The method also preserves the order of the elements in the collection. The syntax of the Guava Ints.toArray() method is as follows:
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public static int[] toArray(Collection<? extends Number> collection) |
The parameter collection is a collection of Number instances, such as Integer, Long, Double, etc. The return value is an int array containing the same values as the collection, in the same order, converted to primitives.
2. Usage of Ints.toArray() method
To use the Guava Ints.toArray() method, you need to import the Ints class from the com.google.common.primitives package. You also need to add the Guava library as a dependency to your project. To demonstrate how to use the Guava Ints.toArray() method, let’s look at some examples.
Example 1: Converting a List<Integer> to an int array
Suppose you have a List<Integer> that contains some integer values. You want to convert it to an int array with the same values and order using the Guava Ints.toArray() method like this:
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import com.google.common.primitives.Ints; import java.util.Arrays; import java.util.List; class Main { public static void main(String[] args) { // Create a list of integers List<Integer> myList = Arrays.asList(1, 2, 3, 4, 5); // Convert it to an int array using Guava Ints.toArray() method int[] arr = Ints.toArray(myList); // Print the array System.out.println(Arrays.toString(arr)); } } |
Example 2: Converting a Set<Long> to an int array
Suppose you have a Set<Long> that contains some long values. You want to convert it to an int array with using the Guava Ints.toArray() method like below. Since sets are unordered collections, the order of the elements in the array may vary depending on the implementation of the set.
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import com.google.common.primitives.Ints; import java.util.Arrays; import java.util.HashSet; import java.util.Set; class Main { public static void main(String[] args) { // Create a set of longs Set<Long> mySet = new HashSet<>(); mySet.add(100L); mySet.add(200L); mySet.add(300L); // Convert it to an int array using Guava Ints.toArray() method int[] arr = Ints.toArray(mySet); // Print the array System.out.println(Arrays.toString(arr)); // [100, 200, 300] } } |
Example 3: Converting a Collection<Double> to an int array
Suppose you have a Collection<Double> that contains some double values. The Ints.toArray() method can convert the collection of doubles to an int array with the same values, but truncated to integers. This is because the method uses the Number.intValue() method to convert each element to an int value, which discards any fractional part.
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import com.google.common.primitives.Ints; import java.util.Arrays; import java.util.Collection; class Main { public static void main(String[] args) { // Create a collection of doubles Collection<Double> myCollection = Arrays.asList(1.5, 2.5, 3.5, 4.5, 5.5); // Convert it to an int array using Guava Ints.toArray() method int[] arr = Ints.toArray(myCollection); // Print the array System.out.println(Arrays.toString(arr)); // [1, 2, 3, 4, 5] } } |
Example 4: Handling null values in the collection
Suppose you have a Collection<Integer> that contains some integer values and some null values. You want to convert it to an int array using the Guava Ints.toArray() method. You can do it like this:
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import com.google.common.primitives.Ints; import java.util.Arrays; import java.util.Collection; class Main { public static void main(String[] args) { // Create a collection of integers and nulls Collection<Integer> myCollection = Arrays.asList(1, null, 3, null, 5); // Convert it to an int array using Guava Ints.toArray() method int[] arr = Ints.toArray(myCollection); // Exception in thread "main" java.lang.NullPointerException } } |
As you can see, the Guava Ints.toArray() method has thrown a NullPointerException when it encountered a null value in the collection. This is because the method does not accept null values as valid elements of the collection. If you want to convert a collection that may contain null values to an int array, you need to handle them before passing them to the method. For example, you can use a stream to filter out null values or replace them with default values.
3. Advantages and Disadvantages
The Ints.toArray() method is a convenient and efficient way to convert a collection of Number instances to an int array with the same values and order. Some of the advantages and disadvantages of using this method are:
Advantages:
- It simplifies the code by avoiding the need to write a loop or use a stream to copy each element from the collection to the array.
- It handles
nullvalues by throwing aNullPointerException, which can prevent unexpected behavior or errors in some cases. - It preserves the order of the elements in the collection, which can be important for some applications or algorithms.
Disadvantages:
- It requires adding the Guava library as a dependency to the project, which can increase the size and complexity of the project.
- It may perform poorly if the collection is large or contains many non-integer values, as it has to convert each element to an int value using the
Number.intValue()method, which may involve rounding or truncating.
4. Conclusion
In this post, we have learned how to convert a collection of numbers to an int array using the Guava Ints.toArray() method in Java. We have seen that this method is a convenient and efficient way to convert any collection of Number instances to an int array with the same values and order. We have also seen how to handle possible null values or exceptions when using this method.
For more information about this method, you can check out the Guava official documentation or its GitHub repository.
Thanks for reading.
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