Arrays in Java | Introduction to Java Arrays | Java Programming | Edureka

2. Topics For Today’s Discussion Topics for Today’s Session Array in Java Types of Arrays Declaring Accessing Updating Creating Working with Array Sorting in Arrays Searching in Arrays JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

3. Java Arrays

4. Java Array Contains collections of homogenous elements It occupies a contiguous memory location All the elements are stored under one variable name Array is a static Data Structure JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

5. Types of Arrays

6. Types Of Arrays 02 01 03 Single Dimensional Two Dimensional Multi Dimensional Single Dimensional or 1-D array is a type of linear array in which elements are stored in a continuous row Two Dimensional or 2-D array is a type of matrix in which elements are stored in rows and columns Multi Dimensional array is a type of nested array JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

7. Working With Arrays

8. Working With Arrays – 1D Declaring and Initializing an One Dimensional Array arrayRefVar = new dataType[arraySize]; = myArray new int[5] datatype[] arrayRefVar = new dataType[arraySize]; = int[5] myArray new int[5] JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

9. Working With Arrays – 1D Declaring and Initializing an One Dimensional Array myArray = myArray[0] 10 myArray[0] myArray[1] myArray[2] myArray[3] myArray[4] JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

10. Working With Arrays – 1D Declaring and Initializing an One Dimensional Array myArray = myArray[1] 20 = myArray[2] 30 10 = myArray[3] 40 myArray[0] myArray[1] myArray[2] myArray[3] myArray[4] = myArray[4] 50 JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

11. Working With Arrays – 1D Declaring and Initializing an One Dimensional Array myArray 10 30 20 40 50 myArray[0] myArray[1] myArray[2] myArray[3] myArray[4] JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

12. Working With Arrays – 1D Declaring and Initializing an One Dimensional Array dataType[] arrayRefVar = new dataType{e1,e2,e3,…,eN}; 20 = 30 40 50 int[] myArray new int{10,20,30,40,50} 10 myArray[0] myArray[1] myArray[2] myArray[3] myArray[4] JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

13. Working With Arrays – 1D Declaring and Initializing an One Dimensional Array dataType[] arrayRefVar = new dataType{e1,e2,e3,…,eN}; int[] myArray 10 30 20 40 50 myArray[0] myArray[1] myArray[2] myArray[3] myArray[4] JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

14. Working With Arrays – 1D Accessing a specific array element arrayRefVar[index] 10 myArray[0] myArray[1] 20 myArray[1] 30 myArray[4] myArray[2] 40 myArray[3] 50 myArray[4] JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

15. Working With Arrays – 1D Accessing a specific array element arrayRefVar[index] 10 myArray[0] myArray[1] myArray[4] 20 myArray[1] 30 myArray[2] Updating a specific array element 40 myArray[3] arrayRefVar[index] = newValue myArray[4] = 100 50 100 myArray[4] JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

16. Working With Arrays – 1D Accessing a specific array element arrayRefVar[index] 10 myArray[0] myArray[1] myArray[4] 20 myArray[1] 30 myArray[2] Updating a specific array element 100 myArray[3] arrayRefVar[index] = newValue myArray[4] = 100 50 myArray[4] JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

17. Working With Arrays – 2D Declaring and Initializing an Two Dimensional Array datatype[][] arrayRefVar = new dataType[row][col]; = int[][] myArray new int[2][2] myArray[0][0] myArray[0][1] = myArray[0][0] 100 myArray[1][0] myArray[1][1] JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

18. Working With Arrays – 2D Declaring and Initializing an Two Dimensional Array datatype[][] arrayRefVar = new dataType[row][col]; = int[][] myArray new int[2][2] = myArray[0][0] myArray[0][1] myArray[0][1] 200 = 100 myArray[1][0] 300 = myArray[1][1] 400 myArray[1][0] myArray[1][1] JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

19. Working With Arrays – 2D Declaring and Initializing an Two Dimensional Array datatype[][] arrayRefVar = new dataType[row][col]; = int[][] myArray new int[2][2] myArray[0][0] myArray[0][1] 100 200 300 400 myArray[1][0] myArray[1][1] JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

20. Working With Arrays – 2D Accessing a specific array element arrayRefVar[row][col] myArray[0][0] myArray[0][1] myArray[0][1] 100 200 Updating a specific array element 300 400 myArray[1][0] myArray[1][1] arrayRefVar[row][col] = newValue myArray[0][1] = 564 564 JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

21. Working With Arrays – 2D Accessing a specific array element arrayRefVar[row][col] myArray[0][0] myArray[0][1] myArray[0][1] 100 564 Updating a specific array element 300 400 myArray[1][0] myArray[1][1] arrayRefVar[row][col] = newValue myArray[0][1] = 564 JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

22. Operations With Arrays Addition of Matrices 1 2 1 1 2 3 5 4 4 5 3 6 1 7 2 7 8 9 a[3][3] b[3][3] JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

23. Operations With Arrays a[3][3] 1 4 2 5 3 6 9 int[][] c = new int[rows][columns]; 7 8 for (int i = 0; i < rows; i++) { 1 5 2 4 1 3 2 for (int j = 0; j < columns; j++) 1 7 { b[3][3] c[i][j] = a[i][j] + b[i][j]; } 2 9 4 9 4 9 11 } 8 15 c[3][3] JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

24. Operations With Arrays 1 2 3 1 2 1 Subtraction 4 5 6 5 4 3 Multiplication Division 7 8 9 1 7 2 b[3][3] a[3][3] JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

25. Sorting in Arrays

26. Sorting in Array Java offers various sorting algorithms that helps in putting elements of a list in a certain order Types of Sorting Algorithms Bubble Sort Insertion Sort Merge Sort Selection Sort Quick Sort JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

27. Bubble Sort Selection Sort Insertion Sort Quick Sort Merge Sort 4 1 10 -3 12 void bubbleSort(int arr[]) { int n = arr.length; for (int i = 0; i < n-1; i++) for (int j = 0; j < n-i-1; j++) if (arr[j] > arr[j+1]) { // swap temp and arr[i] int temp = arr[j]; arr[j] = arr[j+1]; arr[j+1] = temp; } } 4 1 1 1 1 4 4 4 10 -3 12 10 -3 12 10 -3 12 -3 10 12 1 1 1 4 -3 -3 -3 10 12 4 10 12 4 10 12 1 -3 -3 1 4 4 10 12 10 12 -3 1 4 10 12 JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

28. Bubble Sort Selection Sort Insertion Sort Quick Sort Merge Sort void selectionSort(int arr[]) { int n = arr.length; 4 1 10 -3 12 // One by one move boundary of unsorted subarray for (int i = 0; i < n-1; i++) { // Find the minimum element in unsorted array int min_idx = i; for (int j = i+1; j < n; j++) if (arr[j] < arr[min_idx]) min_idx = j; 4 1 10 -3 12 -3 1 10 4 12 -3 1 10 4 12 // Swap the found minimum element with the first element int temp = arr[min_idx]; arr[min_idx] = arr[i]; arr[i] = temp; -3 1 4 10 12 } } JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

29. Bubble Sort Selection Sort Insertion Sort Quick Sort Merge Sort 4 1 10 -3 12 public static int[] insertionSort(int[] input){ 4 1 10 -3 12 int temp; for (int i = 1; i < input.length; i++) { for(int j = i ; j > 0 ; j--){ if(input[j] < input[j-1]){ // Swap with the smallest value temp = input[j]; input[j] = input[j-1]; input[j-1] = temp; } } } return input; 1 4 10 -3 12 1 4 10 -3 12 -3 1 4 10 12 } -3 1 4 10 12 JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

30. Bubble Sort Selection Sort Insertion Sort Quick Sort Merge Sort private void quickSort(int low, int high) { int i = low; int j = high; 2 6 7 4 1 -2 8 4 3 // pivot is middle index int pivot = input[low + (high - low) / 2]; 2 6 7 4 1 -2 8 4 3 // Divide into two arrays while (i <= j) { while (input[i] < pivot) { i++; } while (input[j] > pivot) { j--; } if (i <= j) { swap(i, j); // move index to next position on both sides i++; j--; } } 2 6 7 3 1 -2 8 4 4 2 3 1 6 7 -2 8 4 4 2 3 1 -2 4 6 8 7 4 2 3 1 -2 4 4 8 7 6 JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

31. swap(i, j); // move index to next position on both sides i++; j--; Quick Sort Bubble Sort Selection Sort Insertion Sort Merge Sort } } 2 6 7 4 1 -2 8 4 3 // calls quickSort() method recursively if (low < j) { quickSort(low, j); } 2 6 7 4 1 -2 8 4 3 2 6 7 3 1 -2 8 4 4 if (i < high) { quickSort(i, high); } 2 3 1 6 7 -2 8 4 4 } private void swap(int i, int j) { int temp = input[i]; input[i] = input[j]; input[j] = temp; } 2 3 1 -2 4 6 8 7 4 2 3 1 -2 4 4 8 7 6 } JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

32. Bubble Sort Selection Sort Insertion Sort Quick Sort Merge Sort 4 1 10 -3 12 // Merges two subarrays of arr[] // First subarray is arr[l..m] // Second subarray is arr[m+1..r] void mergeSort(int arr[], int l, int m, int r) { // Find sizes of two subarrays to be merged int n1 = m - l + 1; int n2 = r - m; 4 1 10 -3 12 1 4 10 -3 12 4 1 10 -3 12 /* Create temp arrays */ int L[] = new int [n1]; int R[] = new int [n2]; 1 4 10 -3 12 /*Copy data to temp arrays*/ for (int i=0; i<n1; ++i) L[i] = arr[l + i]; for (int j=0; j<n2; ++j) R[j] = arr[m + 1+ j]; 1 4 10 -3 12 -3 1 4 10 12 JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

33. /*Copy data to temp arrays*/ for (int i=0; i<n1; ++i) L[i] = arr[l + i]; for (int j=0; j<n2; ++j) R[j] = arr[m + 1+ j]; Bubble Sort Selection Sort Insertion Sort Quick Sort Merge Sort 4 1 10 -3 12 /* Merge the temp arrays */ // Initial indexes of first and second subarrays int i = 0, j = 0; 4 1 10 -3 12 // Initial index of merged subarry array int k = l; while (i < n1 && j < n2) { if (L[i] <= R[j]) { arr[k] = L[i]; i++; } else { arr[k] = R[j]; j++; } k++; } 1 4 10 -3 12 4 1 10 -3 12 1 4 10 -3 12 1 4 10 -3 12 -3 1 4 10 12 JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

34. k++; } Bubble Sort Selection Sort Insertion Sort Quick Sort Merge Sort 4 1 10 -3 12 /* Copy remaining elements of L[] if any */ while (i < n1) { arr[k] = L[i]; i++; k++; } 4 1 10 -3 12 1 4 10 -3 12 /* Copy remaining elements of R[] if any */ while (j < n2) { arr[k] = R[j]; j++; k++; } 4 1 10 -3 12 1 4 10 -3 12 1 4 10 -3 12 } -3 1 4 10 12 JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

35. k++; } } Bubble Sort Selection Sort Insertion Sort Quick Sort Merge Sort 4 1 10 -3 12 // Main function that sorts arr[l..r] using // merge() void sort(int arr[], int l, int r) { if (l < r) { // Find the middle point int m = (l+r)/2; 4 1 10 -3 12 1 4 10 -3 12 4 1 10 -3 12 // Sort first and second halves sort(arr, l, m); sort(arr , m+1, r); 1 4 10 -3 12 1 4 10 -3 12 // Merge the sorted halves merge(arr, l, m, r); } -3 1 4 10 12 } JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

36. Searching in Arrays

37. Sorting in Array Java offers various sorting algorithms that helps in putting elements of a list in a certain order Types of Searching Algorithms Linear Search Binary Search JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

38. Linear Search Binary Search 4 static int search(int arr[], int n, int x) { for (int i = 0; i < n; i++) { // Return the index of the element if the element // is found if (arr[i] == x) return i; } 1 10 -3 // return -1 if the element is not found return -1; } 12 JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training

39. Linear Search Binary Search int binarySearch(int arr[], int l, int r, int x) { if (r>=l) { int mid = l + (r - l)/2; // If the element is present at the // middle itself if (arr[mid] == x) return mid; 2 6 7 9 15 26 50 79 83 2 6 7 9 15 26 50 79 83 // If element is smaller than mid, then // it can only be present in left subarray if (arr[mid] > x) return binarySearch(arr, l, mid-1, x); 15 26 50 79 83 // Else the element can only be present // in right subarray return binarySearch(arr, mid+1, r, x); } JAVA CERTIFICATION TRAINING www.edureka.co/java-j2ee-soa-training