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Learn to Code: Java for Absolute Beginners

Arrays with Loops

Explore how to use for and while loops to access and manipulate arrays in Java. Understand looping constructs through examples like generating Fibonacci sequences, checking palindromes, and sorting arrays. Gain hands-on practice writing programs that work with arrays using loops to strengthen your coding skills.

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The for loop with arrays

The individual values in an array are accessed through an index number. The for loop variable can be used as an index number. However, the array values can also be used directly in a for loop.

The following program demonstrates the various ways of accessing array elements:

Java
class Test
{
  public static void main(String[] args) 
  {
    String[] vals = {"-5", "Java", "3.8"};
    System.out.println("One way of printing an array: ");
    for (int i = 0; i < vals.length; i++)
    {
      System.out.println(vals[i]);
    }
    System.out.println("Another way of printing an array: ");
    for (String s: vals)
    {
      System.out.println(s);
    }
  }
}

In the code above:

  • The new item is the vals.length function, which is used to get the length of the array.
  • The first for loop accesses the array values with the help of the loop variable i.
  • The second for loop directly accesses the array values.

The while loop with arrays

We usually use the while loop to deal with arrays when the number of iterations is not fixed. For example, let’s say we want to generate n terms of a Fibonacci sequence and store it in an array, where n is the user input. A Fibonacci sequence is a sequence in which each number is the sum of the two preceding ones, except the first two terms.

Let’s start by noting a few terms of this sequence: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, ….

Here’s how to solve this problem:

  • Start with an empty array of nn
...