Arrays in Java

Introduction

• Presented by Lakshay from Simply Learn.
• Part of a comprehensive Java tutorial series.
• Topics covered: arrays in Java, types of arrays, sorting, and searching in arrays.

What is an Array?

• Data type containing homogeneous elements (same data type).
• A group of like-typed variables referred to by a common name.
• Syntax for declaring an array in Java:

  dataType[] arrayName = new dataType[size];  
  

• Example:
  • Array of integers: int[] arr = new int[5];
• Indexing:
  • Starts at 0. Each element has an associated index.

Features of Arrays

• Dynamically allocated, no need to know memory beforehand.
• All elements stored under one name (array name).
• Contiguous memory allocation (unlike linked lists).

Example: Declaring and Using Arrays

1. Create a new project in IntelliJ, named "Array Program".
2. Code Example:

   int[] arr = new int[5];  
   arr[0] = 10;  
   arr[1] = 20;  
   arr[2] = 30;  
   arr[3] = 40;  
   arr[4] = 50;  
   

3. Printing Elements:
   • Use a for loop:

   for(int i = 0; i < arr.length; i++) {  
       System.out.println("Element at index " + i + " is " + arr[i]);  
   }  
   

4. Error Handling:
   • Adding an extra element causes an "ArrayIndexOutOfBoundsException".

Types of Arrays

1. One-Dimensional Array (Linear Array)
   • Stores data in a single row.
   • Example: int[] arr = new int[5];
2. Two-Dimensional Array
   • Stores data in rows and columns.
   • Example:

   int[][] arr = { {1, 2, 3}, {4, 5, 6} };  
   

3. Multi-Dimensional Array
   • Combination of two or more arrays.

Example: One and Two-Dimensional Arrays

1. One-Dimensional Array:
   • Code to calculate sum of elements.
   • Example: sum += arr[i];
2. Two-Dimensional Array:
   • Use nested for loops to access elements.

   for(int i = 0; i < 2; i++) {  
       for(int j = 0; j < 3; j++) {  
           System.out.print(arr[i][j] + " ");  
       }  
       System.out.println();  
   }  
   

Sorting and Searching Arrays

Sorting

• Use sorting algorithms (e.g., Bubble Sort, Quick Sort).
• Example: Sorting an array of random elements in ascending order.

Searching

• Use searching algorithms (e.g., Linear Search, Binary Search).
• Example: Finding an element in an array, e.g., "11 found at index 5".

Example: Searching and Sorting using Java Code

Binary Search

1. Binary Search Algorithm:
   • Compares target value to middle element.
   • Halves search space until target is found.
2. Code Example:

   int binarySearch(int[] arr, int left, int right, int x) {  
       // Implementation  
   }  
   

Bubble Sort

1. Bubble Sort Algorithm:
   • Compares adjacent pairs, swaps if out of order.
2. Code Example:

   void bubbleSort(int[] arr) {  
       // Implementation  
   }  
   

Conclusion

• Covered arrays, types, sorting, and searching techniques in Java.
• Encouraged practice with examples.