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Java Array Stream: Java Explained

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Java array streams are powerful tools used to read and manipulate data stored in array-like data structures such as arrays. In this article, we’ll explain what Java array streams are and how to use them effectively when writing Java code. We’ll cover potential benefits of using array streams and how to create, filter, sort, aggregate, and reduce the data contained in an array stream. You will also learn how to differentiate between primitive and object types when working with an array stream. Finally, we’ll provide a few code examples of different ways you can use array streams inside your Java applications.

What is Java Array Stream?

A Java array stream is a sequence of elements that can be accessed one at a time. Array streams are created from arrays, and they provide a certain level of flexibility when manipulating the data contained inside the streams. Arrays can provide data in a certain order, whereas streams allow items to be stored in any sequence, with different items being accessed out of order.

Using Java array streams, the programmer has more control over the data elements being accessed without having to alter the actual data being stored in the array. By providing access to the elements contained in an array one at a time, it makes manipulating and performing calculations on the data easier than if it were contained within a single array.

Benefits of Using Java Array Stream

Using Java array streams has several benefits over using traditional arrays. For example, using array streams allows for the manipulation of data without altering the actual structure of the array. A programmer can access elements one at a time and perform calculations or transformations on the data as needed, without changing any of the underlying array data.

Additionally, compared to traditional arrays, array streams also provide more efficient memory usage. Rather than having to store all the elements at once in memory, stream elements are loaded when needed, saving on resources. This makes it ideal for applications that rely on access to large data sets.

How to Create an Array Stream in Java

Creating an array stream in Java is simple. All you need to do is pass in the array that you want to work with as an argument to the stream() method. This method will return a new stream object with references to all the elements of the array. For example:

int[] myArray = {1, 2, 3};Stream<int> myArrayStream = Arrays.stream(myArray);

Once you have your array stream, you are free to read and manipulate the data contained within it.

Converting from an Array to a Stream in Java

There are two ways to convert from an array to a stream in Java: using the stream() method or using the of() method. The stream() method takes an array of primitives or objects as an argument and returns a new stream object. For example, if you were working with an array of integers, you would pass your array into stream():

int[] myArray = {1, 2, 3}; Stream<int> myArrayStream = Arrays.stream(myArray);

The of() method creates a stream from a variable number of arguments. It’s most useful when creating a stream from a smaller amount of primitive values. For example:

Stream<int> myArrayStream = Stream.of(1, 2, 3);

Filtering an Array Stream in Java

To filter an array stream, you can use the filter() method. This method takes in a predicate as an argument and will return a new stream object that contains only the elements that meet the criteria specified by the predicate.

For example, if you wanted to filter out all numbers larger than 10 from an integer array stream, you would write the following code:

int[] myArray = {1, 2, 3, 11, 12, 13}; Stream<int> myArrayStream = Arrays.stream(myArray); myArrayStream = myArrayStream.filter(x -> x <= 10);

The new myArrayStream will now contain only integers larger than 10.

Sorting an Array Stream in Java

To sort an array stream in Java, you can use the sorted() method. This method takes a comparator as an argument and returns a new stream object with all the elements sorted according to the criteria specified by the comparator. For example, if you wanted to sort your integer array stream in ascending order, you would write the following code:

int[] myArray = {1, 2, 3, 11, 12, 13}; Stream<int> myArrayStream = Arrays.stream(myArray); myArrayStream = myArrayStream.sorted(Comparator.naturalOrder());

Now your myArrayStream will contain all the integers sorted in ascending order.

Aggregating Data from an Array Stream in Java

To aggregate data from an array stream in Java, you can use the collect() method. This method takes a collector as an argument and returns a new object with all the data contained within your stream aggregated into a single value. This is useful for performing calculations on the elements of the stream without having to loop through each individual element.

For example, if you wanted to sum up all the elements from your integer array stream, you could easily do so by writing:

int[] myArray = {1, 2, 3, 11, 12, 13}; Stream<int> myArrayStream = Arrays.stream(myArray); int sum = myArrayStream.collect(Collectors.summingInt(x -> x));

The new sum variable will now contain the sum of all elements in your integer stream.

Reducing an Array Stream in Java

To reduce an array stream in Java, you can use the reduce() method. This method takes two arguments: an initial value and a binary operator that takes two elements of type T and returns a single element of type T. The .reduce() method then applies the binary operator to all elements of the stream and returns a single reduced value.

For example, if your integer array stream has the numbers 1 – 4, and you want to multiply all these numbers together and create a single output value:

int[] myArray = {1, 2, 3, 4}; Stream<int> myArrayStream = Arrays.stream(myArray); int outputNum = myArrayStream.reduce(1 , (x,y) -> x*y);

The new outputNum variable will now contain the result of multiplying together 1 * 2 * 3 * 4.

Working with Primitive Arrays and Wrapper Classes

When working with Java array streams, it is important to be aware of which type of array you are working with. Primitive arrays contain values of primitive types such as int, long, double, etc., while wrapper class arrays contain references to objects created from their corresponding primitive types.

For example:

int[] myIntArray = {1,2,3} // primitive array  Integer[] myIntegerArray = {1,2,3} // wrapper class array

  • When using methods like .filter(), .sorted(), .collect(), and .reduce(), it is important to take into account whether or not you are working with primitive or wrapper class arrays. Depending on which type of array you are working with, you will need to use different methods or pass arguments into certain methods as appropriate.

  • For example: If you were working with an array of integers and wanted to sum up all the values in the array using .collect(), you would need to use the .summingInt() collector if you are working with a primitive int array or the .summingInteger(), if you are working with an objects array (or .Integer[]). If you don’t take into account what type of array you are working with when writing your code, then it won’t compile. ).

    Examples of Using Java Array Streams

    For example:

    1. To filter out all numbers larger than 10 from your integer array stream:
      1. int[] myArray = {1, 2, 3, 11, 12, 13};  Stream<int> myArrayStream = Arrays.stream(myArray);  myArrayStream = myArrayStream.filter(x -> x <= 10);
      2. To sort your integer array stream in ascending order:

        1. int[] myArray = {1, 2, 3, 11, 12, 13};  Stream<int> myArrayStream = Arrays.stream(myArray);  myArrayStream = myArrayStream.sorted(Comparator.naturalOrder());
        2. To sum up all elements from your integer array stream:

          1. int[] myArray = {1, 2, 3, 11, 12, 13};  Stream<int> myArrayStream = Arrays.stream(myArray);  int sum = myArrayStream.collect(Collectors.summingInt(x -> x));
          2. To multiply together all elements from your integer array stream:

            1. int[] myArray = {1, 2, 3};  Stream<int> myArrayStream = Arrays.stream(myArray);  int outputNum = myArrayStream.reduce(1 , (x,y) -> x*y); 
            2. These are just a few of many examples of how you can make use of Java array streams within your applications.

              We hope that this article has helped you gain a better understanding of Java array streams and how they can be used to read and manipulate data more efficiently within your applications.

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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