Array Class in Java
Java provides the java.util.Arrays class to handle various array-related operations. This class offers methods for manipulating, searching, and sorting elements of an array. The Arrays class in Java serves as a utility class to work with arrays, making it easier to perform common operations.
Below are the commonly used methods of the Arrays class:
Sort Array
It is used to arrange array data in ascending order.
import java.util.Arrays;
public class Main {
public static void main(String[] args) {
int[] numbers = { 4, 2, 8, 1, 6 };
Arrays.sort(numbers);
for (int item : numbers) {
System.out.print(item + ” “); // Output will be 1 2 4 6 8
}
}
}
ForEach
Java 8 introduced the forEach method, which can be used to perform a specified action on each element of the array.
import java.util.Arrays;
public class Main {
public static void main(String[] args) {
int[] numbers = { 10, 20, 30, 40, 50 };
Arrays.stream(numbers).forEach(n -> System.out.println(n * 2));
// Output: 20, 40, 60, 80, 100
}
}
Copying Array
You can copy elements from one array to another array.
import java.util.Arrays;
public class Main {
public static void main(String[] args) {
int[] source = {40, 35, 70, 20, 55};
int[] destination = Arrays.copyOfRange(source, 0, 4);
for (int item : destination) {
System.out.println(item); // Output will be 40, 35, 70, 20
}
// Note: The destination array has 4 elements, so it copies the first 4 elements from source.
}
}
Equals Array
Check whether both array values and index are equal or not using a Boolean output.
import java.util.Arrays;
public class Main {
public static void main(String[] args) {
int[] firstArray = { 40, 20, 30, 45 };
int[] secondArray = { 40, 30, 20, 45 };
boolean areEqual = Arrays.equals(firstArray, secondArray);
System.out.println(areEqual); // Output will be False as the index of the values is not the same.
}
}
Convert Array to List
Arrays have a fixed size, which means once you define the size of an array, you cannot change it. However, lists (List<T>) are dynamic, meaning you can add or remove elements as needed without worrying about size limitations.
import java.util.Arrays;
import java.util.List;
public class Main {
public static void main(String[] args) {
// Define an array
Integer[] numbersArray = { 10, 20, 30, 40, 50 };
// Convert the array to a list
List<Integer> numbersList = Arrays.asList(numbersArray);
// Convert to mutable list
List<Integer> mutableList = new ArrayList<>(numbersList);
// Add an element to the list
mutableList.add(25);
// Remove an element from the list
mutableList.remove(Integer.valueOf(20));
// Print the list elements
System.out.println(“List elements:”);
for (int number : mutableList) {
System.out.println(number);
}
}
}
Output:
List elements:
10
30
40
50
25
Example: Using an Array with an If-Else Statement
Here is a simple example of using an array with an if-else statement in Java. In this example, we create an array of numbers and check if each number is even or odd using an if-else statement.
public class Main {
public static void main(String[] args) {
int[] numbers = { 10, 5, 8, 3, 12 };
for (int num : numbers) {
if (num % 2 == 0) {
System.out.println(num + ” is even.”);
} else {
System.out.println(num + ” is odd.”);
}
}
}
}
Explanation:
public class Main {
public static void main(String[] args) {
int[] numbers = { 10, 5, 8, 3, 12 };
// Define an array of integers with specific values
for (int num : numbers)
// Iterate through each element in the numbers array
{
if (num % 2 == 0)
// Check if the current number is even (remainder of division by 2 is 0)
{
System.out.println(num + ” is even.”);
// Print that the number is even using string concatenation
} else
// If the number is not even
{
System.out.println(num + ” is odd.”);
// Print that the number is odd using string concatenation
}
}
}
}
Tasks:
1. Sort an Array: Create an integer array with the values {3, 1, 4, 1, 5, 9}. Use Arrays.sort to sort the array and print the sorted values.
2. Double Each Element: Create an integer array with the values {1, 2, 3, 4, 5}. Use a loop to double each element and print the modified array.
3. Copy Array: Create a source integer array with the values {11, 22, 33, 44, 55}. Create a destination array of size 3. Use System.arraycopy to copy the first 3 elements from the source to the destination and print the destination array.
4. Check Equality: Create two integer arrays, one with the values {5, 10, 15} and the other with the values {5, 10, 15}. Use Arrays.equals to check if the arrays are equal and print the result.
5. Even or Odd Check: Create an integer array with the values {7, 14, 21, 28, 35}. Use a loop and an if-else statement to check if each number is even or odd, and print the result.
6. Sort and Print Strings: Create a string array with the values {“banana”, “apple”, “cherry”}. Use Arrays.sort to sort the array alphabetically and print the sorted values.
7. Find and Print Even Numbers: Create an integer array with the values {12, 15, 18, 21, 24}. Use a loop and an if-else statement to print only the even numbers from the array.
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