Java Array Methods
Built-in methods for working with arrays and collections
📚 What are Array Methods?
Array methods are built-in functions that help you manipulate, search, and organize collections of data in Java. They make working with multiple values simple and efficient.
// Basic array methods example
import java.util.Arrays;
int[] numbers = {3, 1, 4, 1, 5};
Arrays.sort(numbers); // Sort array
System.out.println(Arrays.toString(numbers)); // [1, 1, 3, 4, 5]
System.out.println(numbers.length); // 5
Types of Array Methods
Basic Properties
Get information about arrays
Search & Find
Find elements in arrays
Sort & Organize
Arrange array elements
Copy & Fill
Create and modify arrays
🔹 Basic Array Properties
Get essential information about your arrays:
import java.util.Arrays;
public class ArrayBasics {
public static void main(String[] args) {
int[] numbers = {10, 20, 30, 40, 50};
String[] names = {"Alice", "Bob", "Charlie"};
// Get array length
System.out.println("Numbers length: " + numbers.length);
System.out.println("Names length: " + names.length);
// Convert array to string for display
System.out.println("Numbers: " + Arrays.toString(numbers));
System.out.println("Names: " + Arrays.toString(names));
// Access individual elements
System.out.println("First number: " + numbers[0]);
System.out.println("Last name: " + names[names.length - 1]);
}
}Output:
Numbers length: 5
Names length: 3
Numbers: [10, 20, 30, 40, 50]
Names: [Alice, Bob, Charlie]
First number: 10
Last name: Charlie
🔹 Sorting and Organizing Arrays
Arrange your array elements in different orders:
import java.util.Arrays;
import java.util.Collections;
public class ArraySorting {
public static void main(String[] args) {
Integer[] scores = {85, 92, 78, 96, 88};
String[] fruits = {"banana", "apple", "cherry", "date"};
// Sort numbers in ascending order
Arrays.sort(scores);
System.out.println("Sorted scores: " + Arrays.toString(scores));
// Sort strings alphabetically
Arrays.sort(fruits);
System.out.println("Sorted fruits: " + Arrays.toString(fruits));
// Sort in descending order
Arrays.sort(scores, Collections.reverseOrder());
System.out.println("Descending scores: " + Arrays.toString(scores));
}
}Output:
Sorted scores: [78, 85, 88, 92, 96]
Sorted fruits: [apple, banana, cherry, date]
Descending scores: [96, 92, 88, 85, 78]
🔹 Searching in Arrays
Find specific elements in your arrays:
import java.util.Arrays;
public class ArraySearch {
public static void main(String[] args) {
int[] numbers = {10, 20, 30, 40, 50};
String[] colors = {"red", "blue", "green", "yellow"};
// Linear search (manual)
int target = 30;
int position = -1;
for (int i = 0; i < numbers.length; i++) {
if (numbers[i] == target) {
position = i;
break;
}
}
System.out.println(target + " found at position: " + position);
// Binary search (array must be sorted)
Arrays.sort(numbers);
int index = Arrays.binarySearch(numbers, 40);
System.out.println("Binary search for 40: " + index);
// Check if array contains element (using Arrays.asList)
boolean hasBlue = Arrays.asList(colors).contains("blue");
System.out.println("Contains 'blue': " + hasBlue);
}
}Output:
30 found at position: 2
Binary search for 40: 3
Contains 'blue': true
🔹 Copying and Filling Arrays
Create new arrays and fill them with values:
import java.util.Arrays;
public class ArrayCopyFill {
public static void main(String[] args) {
int[] original = {1, 2, 3, 4, 5};
// Copy entire array
int[] copy1 = Arrays.copyOf(original, original.length);
System.out.println("Full copy: " + Arrays.toString(copy1));
// Copy part of array
int[] copy2 = Arrays.copyOfRange(original, 1, 4);
System.out.println("Partial copy: " + Arrays.toString(copy2));
// Create and fill array
int[] filled = new int[5];
Arrays.fill(filled, 99);
System.out.println("Filled array: " + Arrays.toString(filled));
// Fill part of array
int[] partial = {1, 2, 3, 4, 5};
Arrays.fill(partial, 1, 4, 0);
System.out.println("Partially filled: " + Arrays.toString(partial));
}
}Output:
Full copy: [1, 2, 3, 4, 5]
Partial copy: [2, 3, 4]
Filled array: [99, 99, 99, 99, 99]
Partially filled: [1, 0, 0, 0, 5]
🔹 Comparing Arrays
Check if arrays are equal or compare their contents:
import java.util.Arrays;
public class ArrayComparison {
public static void main(String[] args) {
int[] array1 = {1, 2, 3, 4, 5};
int[] array2 = {1, 2, 3, 4, 5};
int[] array3 = {5, 4, 3, 2, 1};
// Compare arrays for equality
System.out.println("array1 equals array2: " + Arrays.equals(array1, array2));
System.out.println("array1 equals array3: " + Arrays.equals(array1, array3));
// Compare arrays lexicographically
System.out.println("Compare array1 to array3: " + Arrays.compare(array1, array3));
// Hash code for arrays
System.out.println("Hash code of array1: " + Arrays.hashCode(array1));
System.out.println("Hash code of array2: " + Arrays.hashCode(array2));
}
}Output:
array1 equals array2: true
array1 equals array3: false
Compare array1 to array3: -1
Hash code of array1: 29615266
Hash code of array2: 29615266
🔹 Practical Array Examples
Real-world applications of array methods:
Common Use Cases:
- Student grades: Sort and find highest/lowest scores
- Inventory: Search for products, organize by price
- Data analysis: Find duplicates, calculate statistics
- Gaming: High score lists, player rankings
import java.util.Arrays;
public class PracticalArrays {
public static void main(String[] args) {
// Student grades example
int[] grades = {85, 92, 78, 96, 88, 92, 85};
// Find highest and lowest grades
Arrays.sort(grades);
System.out.println("Lowest grade: " + grades[0]);
System.out.println("Highest grade: " + grades[grades.length - 1]);
// Calculate average
int sum = 0;
for (int grade : grades) {
sum += grade;
}
double average = (double) sum / grades.length;
System.out.println("Average grade: " + Math.round(average * 100.0) / 100.0);
// Count occurrences of a grade
int target = 92;
int count = 0;
for (int grade : grades) {
if (grade == target) count++;
}
System.out.println("Students with grade " + target + ": " + count);
}
}