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Learn Java: Arrays
Introduction

We have seen how to store single pieces of data in variables. What happens when we need to store a group of data? What if we have a list of students in a classroom? Or a ranking of the top 10 horses finishing a horse race?

If we were storing 5 lottery ticket numbers, for example, we could create a different variable for each value:

int firstNumber = 4; int secondNumber = 8; int thirdNumber = 15; int fourthNumber = 16; int fifthNumber = 23;

That is a lot of ungainly repeated code. What if we had a hundred lottery numbers? It is more clean and convenient to use a Java array to store the data as a list.

An array holds a fixed number of values of one type. Arrays hold doubles, ints, booleans, or any other primitives. Arrays can also contain Strings, or any other objects!

Each index of an array corresponds with a different value. Here is a diagram of an array filled with integer values:

A diagram of an example int array

Notice that the indexes start at 0! The element at index 0 is 4, while the element at index 1 is 8. This array has a length of 5, since it holds five elements, but the highest index of the array is 4.

Let’s explore how to create and use arrays in Java, so that we can store all of our Java data types.

Instructions

1.

In Newsfeed.java, we have created a Newsfeed class to keep track of trending articles and their associated views and ratings. We did this using Java arrays, which you’ll learn about throughout the lesson!

For now, run the code to see some of our method calls.

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