Java tutorials

docs/java/arrays-and-collections/array-lists-and-collections-framework.md

@@ -5,4 +5,150 @@ sidebar_label: ArrayLists and Collections Framework
 sidebar_position: 2
 tags: [java, array-lists-and-collections-framework]
 description: In this tutorial, you will learn about ArrayLists and the Collections Framework in Java.
----
+---
+
+# ArrayLists and the Collections Framework in Java
+
+## Introduction
+
+Java's Collections Framework provides a set of classes and interfaces for storing and manipulating groups of data as a single unit. `ArrayList` is one of the most commonly used classes in this framework, offering dynamic arrays that can grow and shrink in size.
+
+## ArrayList
+
+An `ArrayList` is a resizable array that provides more functionality and flexibility compared to a standard array. It is part of the `java.util` package.
+
+### Declaration
+
+To use `ArrayList`, you need to import it from the `java.util` package.
+
+### Syntax
+
+```java
+import java.util.ArrayList;
+
+ArrayList<dataType> arrayListName = new ArrayList<>();
+```
+
+### Example
+
+```java
+import java.util.ArrayList;
+
+public class Main {
+    public static void main(String[] args) {
+        ArrayList<String> names = new ArrayList<>();
+
+        // Adding elements
+        names.add("Alice");
+        names.add("Bob");
+        names.add("Charlie");
+
+        // Accessing elements
+        System.out.println(names.get(0)); // Outputs: Alice
+
+        // Modifying elements
+        names.set(1, "Robert");
+
+        // Removing elements
+        names.remove(2);
+
+        // Iterating over the ArrayList
+        for (String name : names) {
+            System.out.println(name);
+        }
+    }
+}
+```
+
+### Common Methods
+
+- `add(element)`: Adds an element to the end of the list.
+- `add(index, element)`: Inserts an element at the specified index.
+- `get(index)`: Returns the element at the specified index.
+- `set(index, element)`: Replaces the element at the specified index with the specified element.
+- `remove(index)`: Removes the element at the specified index.
+- `remove(element)`: Removes the first occurrence of the specified element.
+- `size()`: Returns the number of elements in the list.
+- `clear()`: Removes all elements from the list.
+- `isEmpty()`: Returns `true` if the list contains no elements.
+
+## Collections Framework
+
+The Collections Framework provides a unified architecture for representing and manipulating collections. It includes interfaces, implementations, and algorithms.
+
+### Interfaces
+
+- `Collection`: The root interface for all collections.
+- `List`: An ordered collection (also known as a sequence). `ArrayList` and `LinkedList` are its implementations.
+- `Set`: A collection that contains no duplicate elements. `HashSet` and `TreeSet` are its implementations.
+- `Queue`: A collection used to hold multiple elements prior to processing. `LinkedList` and `PriorityQueue` are its implementations.
+- `Map`: An object that maps keys to values. `HashMap` and `TreeMap` are its implementations.
+
+### Example: Using Different Collections
+
+```java
+import java.util.*;
+
+public class Main {
+    public static void main(String[] args) {
+        // List example
+        List<String> list = new ArrayList<>();
+        list.add("Apple");
+        list.add("Banana");
+        list.add("Orange");
+        System.out.println("List: " + list);
+
+        // Set example
+        Set<String> set = new HashSet<>();
+        set.add("Apple");
+        set.add("Banana");
+        set.add("Apple"); // Duplicate element will not be added
+        System.out.println("Set: " + set);
+
+        // Queue example
+        Queue<String> queue = new LinkedList<>();
+        queue.add("Apple");
+        queue.add("Banana");
+        queue.add("Orange");
+        System.out.println("Queue: " + queue);
+        System.out.println("Queue poll: " + queue.poll()); // Removes and returns the head of the queue
+
+        // Map example
+        Map<String, Integer> map = new HashMap<>();
+        map.put("Apple", 1);
+        map.put("Banana", 2);
+        map.put("Orange", 3);
+        System.out.println("Map: " + map);
+        System.out.println("Map get: " + map.get("Banana")); // Returns the value for the specified key
+    }
+}
+```
+
+### Algorithms
+
+The `Collections` class provides static methods that operate on collections, such as sorting and searching.
+
+#### Example: Sorting a List
+
+```java
+import java.util.*;
+
+public class Main {
+    public static void main(String[] args) {
+        List<String> list = new ArrayList<>();
+        list.add("Banana");
+        list.add("Apple");
+        list.add("Orange");
+
+        Collections.sort(list); // Sorts the list in natural order
+        System.out.println("Sorted List: " + list);
+
+        Collections.sort(list, Collections.reverseOrder()); // Sorts the list in reverse order
+        System.out.println("Reverse Sorted List: " + list);
+    }
+}
+```
+
+## Conclusion
+
+The Collections Framework in Java provides a powerful and flexible set of classes and interfaces for managing groups of objects. `ArrayList` is a versatile and commonly used class within this framework. Understanding how to use `ArrayList` and other collections, as well as the algorithms provided by the `Collections` class, is crucial for effective Java programming.

docs/java/arrays-and-collections/arrays-in-java.md

@@ -5,4 +5,161 @@ sidebar_label: Arrays in Java
 sidebar_position: 1
 tags: [java, arrays, programming, java arrays]
 description: In this tutorial, we will learn about arrays in Java. We will learn about what arrays are, how to declare and initialize arrays, how to access elements in an array, and how to use arrays in Java.
----
+---
+
+# Arrays in Java
+
+## Introduction
+
+Arrays in Java are used to store multiple values of the same type in a single variable, instead of declaring separate variables for each value. Arrays are a fundamental data structure that can help in organizing and managing data efficiently.
+
+## Array Declaration
+
+### Syntax
+
+To declare an array, specify the data type followed by square brackets and the array name.
+
+```java
+dataType[] arrayName;
+```
+
+### Example
+
+```java
+int[] numbers;
+String[] names;
+```
+
+## Array Initialization
+
+### Static Initialization
+
+You can initialize an array at the time of declaration with a set of values.
+
+```java
+int[] numbers = {1, 2, 3, 4, 5};
+String[] names = {"Alice", "Bob", "Charlie"};
+```
+
+### Dynamic Initialization
+
+You can also allocate memory for the array using the `new` keyword and then assign values to the array elements.
+
+```java
+int[] numbers = new int[5]; // Array of 5 integers
+numbers[0] = 1;
+numbers[1] = 2;
+numbers[2] = 3;
+numbers[3] = 4;
+numbers[4] = 5;
+```
+
+## Accessing Array Elements
+
+Array elements are accessed using their index, which starts from 0.
+
+### Example
+
+```java
+int[] numbers = {1, 2, 3, 4, 5};
+System.out.println(numbers[0]); // Outputs: 1
+System.out.println(numbers[4]); // Outputs: 5
+```
+
+## Looping Through Arrays
+
+### For Loop
+
+You can use a `for` loop to iterate through all the elements of an array.
+
+```java
+int[] numbers = {1, 2, 3, 4, 5};
+for (int i = 0; i < numbers.length; i++) {
+    System.out.println(numbers[i]);
+}
+```
+
+### Enhanced For Loop (For-Each Loop)
+
+The enhanced `for` loop provides a simpler way to iterate through the elements of an array.
+
+```java
+int[] numbers = {1, 2, 3, 4, 5};
+for (int number : numbers) {
+    System.out.println(number);
+}
+```
+
+## Multi-Dimensional Arrays
+
+Java supports multi-dimensional arrays, which are arrays of arrays.
+
+### Two-Dimensional Array
+
+#### Declaration and Initialization
+
+```java
+int[][] matrix = {
+    {1, 2, 3},
+    {4, 5, 6},
+    {7, 8, 9}
+};
+```
+
+#### Accessing Elements
+
+```java
+System.out.println(matrix[0][0]); // Outputs: 1
+System.out.println(matrix[2][2]); // Outputs: 9
+```
+
+#### Looping Through a Two-Dimensional Array
+
+```java
+for (int i = 0; i < matrix.length; i++) {
+    for (int j = 0; j < matrix[i].length; j++) {
+        System.out.print(matrix[i][j] + " ");
+    }
+    System.out.println();
+}
+```
+
+### Example: Matrix Addition
+
+```java
+public class MatrixAddition {
+    public static void main(String[] args) {
+        int[][] matrix1 = {
+            {1, 2, 3},
+            {4, 5, 6},
+            {7, 8, 9}
+        };
+
+        int[][] matrix2 = {
+            {9, 8, 7},
+            {6, 5, 4},
+            {3, 2, 1}
+        };
+
+        int[][] sum = new int[3][3];
+
+        for (int i = 0; i < matrix1.length; i++) {
+            for (int j = 0; j < matrix1[i].length; j++) {
+                sum[i][j] = matrix1[i][j] + matrix2[i][j];
+            }
+        }
+
+        // Display the result
+        for (int[] row : sum) {
+            for (int element : row) {
+                System.out.print(element + " ");
+            }
+            System.out.println();
+        }
+    }
+}
+```
+
+## Conclusion
+
+Arrays are a powerful and essential feature in Java, allowing you to store and manage collections of data efficiently. Understanding how to declare, initialize, and manipulate arrays, as well as how to use multi-dimensional arrays, is crucial for effective Java programming.