Implementing Arrays and String Functions in Java

 

1️⃣ Working with Arrays in Java

An array in Java is a collection of elements of the same type, stored in contiguous memory locations.

🔹 Declaring and Initializing an Array:

public class ArrayExample {
    public static void main(String[] args) {
        int[] numbers = {10, 20, 30, 40, 50};  // Array declaration and initialization
        System.out.println("First element: " + numbers[0]);  // Accessing array elements
        
        // Using a loop to print all elements
        System.out.println("Array Elements:");
        for (int num : numbers) {
            System.out.println(num);
        }
    }
}

✅ Output:

First element: 10
Array Elements:
10
20
30
40
50

---

🔹 Taking Array Input from User and Finding Sum:

import java.util.Scanner;

public class ArrayInput {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        System.out.print("Enter number of elements: ");
        int n = sc.nextInt();  // Taking input for array size
        
        int[] arr = new int[n];  // Declaring array
        int sum = 0;
        
        // Taking input in array
        System.out.println("Enter " + n + " numbers:");
        for (int i = 0; i < n; i++) {
            arr[i] = sc.nextInt();
            sum += arr[i];  // Calculating sum
        }
        
        System.out.println("Sum of elements: " + sum);
        sc.close();
    }
}

✅ Example Output:

Enter number of elements: 3
Enter 3 numbers:
5
10
15
Sum of elements: 30

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2️⃣ String Functions in Java

A string in Java is a sequence of characters, handled using the String class.

🔹 Basic String Operations:

public class StringExample {
    public static void main(String[] args) {
        String str = "Hello, Java!";
        
        System.out.println("Original String: " + str);
        System.out.println("Length: " + str.length());
        System.out.println("Character at index 1: " + str.charAt(1));
        System.out.println("Substring (0 to 5): " + str.substring(0, 5));
        System.out.println("Uppercase: " + str.toUpperCase());
        System.out.println("Lowercase: " + str.toLowerCase());
        System.out.println("Replaced 'Java' with 'World': " + str.replace("Java", "World"));
    }
}

✅ Output:

Original String: Hello, Java!
Length: 12
Character at index 1: e
Substring (0 to 5): Hello
Uppercase: HELLO, JAVA!
Lowercase: hello, java!
Replaced 'Java' with 'World': Hello, World!

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🔹 Concatenating and Comparing Strings:

public class StringOperations {
    public static void main(String[] args) {
        String s1 = "Hello";
        String s2 = "World";
        
        // Concatenation
        String s3 = s1 + " " + s2;
        System.out.println("Concatenated String: " + s3);
        
        // Comparing strings
        String str1 = "Java";
        String str2 = "java";
        System.out.println("Are str1 and str2 equal? " + str1.equals(str2));
        System.out.println("Ignoring case, are str1 and str2 equal? " + str1.equalsIgnoreCase(str2));
    }
}

✅ Output:

Concatenated String: Hello World
Are str1 and str2 equal? false
Ignoring case, are str1 and str2 equal? true

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🔹 Checking if a String is Palindrome:

import java.util.Scanner;

public class PalindromeCheck {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter a string: ");
        String str = sc.nextLine();
        
        String reversed = new StringBuilder(str).reverse().toString();
        
        if (str.equalsIgnoreCase(reversed)) {
            System.out.println("The string is a palindrome.");
        } else {
            System.out.println("The string is not a palindrome.");
        }
        sc.close();
    }
}

✅ Example Output:

Enter a string: madam
The string is a palindrome.

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Conclusion

✅ Arrays help store multiple values in a single variable.
✅ Strings provide many useful functions like concatenation, substring, replacement, and comparison.
✅ Java provides built-in methods to handle both arrays and strings efficiently.

🚀 Next Steps:

• Learn multidimensional arrays.
• Work with StringBuilder for faster string manipulations.
• Explore sorting and searching techniques on arrays.