Question

a) Write a statement that declares a string array initialized with the following strings: "Mercury", "Venus", "Earth", and "Mars". b) Write a loop that displays the contents of cach element in the array you declared in A. c) Write a loop that displays the first character of the strings stored in cach element of the array you declared in A. (Hint: Use the string class's charat method discussed in Chaprer \(2 .\)

Short answer

Question: Declare a string array initialized with the following strings: "Mercury", "Venus", "Earth", and "Mars". Then write a loop to display the contents of each element and another loop to display the first character of each string. Answer: Here's the code to create the string array, display its contents, and display the first character of each string: ```java // Declare and initialize the string array String[] planets = {"Mercury", "Venus", "Earth", "Mars"}; // Display the contents of the array for (String planet : planets) { System.out.println(planet); } // Display the first character of each string for (String planet : planets) { System.out.println(planet.charAt(0)); } ```

Step-by-step solution

Declare and Initialize the String Array

To declare and initialize a string array with the strings "Mercury", "Venus", "Earth", and "Mars", you would use the following statement: ```java String[] planets = {"Mercury", "Venus", "Earth", "Mars"}; ``` In this step, a string array named `planets` is both declared and initialized with the given planet names. #exercise# b) Write a loop that displays the contents of each element in the array you declared in A.

Display the Contents of the Array

To display the names of the planets from the `planets` array, use a for-loop that iterates through the entire array and print each element. Here's how to do this: ```java for (String planet : planets) { System.out.println(planet); } ``` In this step, a for-each loop is used, going through each element in the 'planets' array and printing the name of the planet. #exercise# c) Write a loop that displays the first character of the strings stored in each element of the array you declared in A. (Hint: Use the string class's charAt method discussed in Chapter 2.)

Display the First Character of Each String

To display the first character of each string in the `planets` array, you will use a for-loop again, but this time, you'll apply the `charAt()` method to each string in the array. Here's how to do this: ```java for (String planet : planets) { System.out.println(planet.charAt(0)); } ``` In this step, a for-each loop goes through the 'planets' array, and for each of the planet names, it prints the first character using the `charAt(0)` method.

Key concepts

String Array Initialization

In Java, arrays are powerful tools used to store multiple values of the same type. Initializing a string array is straightforward.
To declare a string array and initialize it simultaneously, you use the following syntax: ```java String[] planets = {"Mercury", "Venus", "Earth", "Mars"}; ``` This statement does a few things:

• It declares an array named `planets`.
• It initializes it with four string elements: "Mercury", "Venus", "Earth", and "Mars".

By combining these two steps, you not only save time but also ensure that the array has the correct size to hold your initial values. Initializations can happen in various contexts, such as class variables or local variables, and this approach helps keep the code clean and easy to read.

For-Each Loop

The for-each loop, also known as the enhanced for loop, is a more concise way to traverse through arrays in Java.
It simplifies the process of iterating over elements, making your code easier to write and read. Here's how it looks when used to print every element in the `planets` array: ```java for (String planet : planets) { System.out.println(planet); } ``` Let's break this down:

• `for (String planet : planets)`: This part tells the loop to grab each `String` from the `planets` array and refer to it as `planet`.
• `System.out.println(planet);`: This command prints the current planet.

Using a for-each loop removes the need for manual index management, reducing errors and improving code readability.
It’s essential for cases where you just need to access each element, not modify them or manage multiple indices.

charAt Method

Strings in Java are objects, which means they come with a set of built-in methods.
One of these methods is `charAt()`, which retrieves a character from a specific index of a string. Consider this example, where it is used to print the first character of each planet: ```java for (String planet : planets) { System.out.println(planet.charAt(0)); } ``` Here's how the `charAt` method works:

• `planet.charAt(0)`: This calls the `charAt` method on the `planet` string to access the character at index `0`.
• The index `0` is specified because arrays and strings are zero-indexed in Java, meaning the first position is index `0`.

Using `charAt(0)`, you efficiently get the first character of each string in an array.
This method is invaluable when you need to access specific characters within each string, helping in tasks such as validation or format checks.

Programming Exercises

Programming exercises are designed to improve problem-solving skills.
By writing and debugging code, you can deepen your understanding of programming concepts. This exercise of managing arrays, loops, and string methods in Java covers foundational programming skills:

• Array Management: Understanding how to declare and initialize arrays is crucial as they are a staple of programming.
• Loop Structures: Using loops like the for-each loop helps automate repetitive tasks effectively.
• String Handling: Methods like `charAt()` show how to manipulate and access parts of strings.

By practicing these exercises, you become familiar with handling collection data types, manipulating data efficiently, and improving your logic-building skills.
Ultimately, these fundamental skills gained from programming exercises are applicable across diverse coding challenges and real-world applications.