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# Chapter 7.3

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### Transcript

• 1. MANIPULATING ARRAY AS PARAMETERS TO METHODS Chapter 7.3:
• 2. Arrays as Formal Parameters to Methods Arrays can be passed as parameter to methods Eg. public static void arrayAsFormalParameter(int[] listA, double[] listB, int num) { //… } Formal parameter The above method have 3 formal parameters – listA, listB and num
• 3. continue Statement to call the method arrayAsFormalParameter(intList, doubleNumList, number); Actual parameter int[] intList = new int[10]; double[] doubleNumList = new double[15]; int number; Suppose we have the following statement
• 4. example 1 public class PassingParameter { public static void main(String[] args) { int num[] = {10,20,30,40,50,60,70}; System.out.println(“ The number of elements: " + num.length); printArray(num); } public static void printArray(int[] number) { for (int index = 0; index < number.length; index++) System.out.println(number[index] + ""); } } Passing parameter OUTPUT: The number of elements: 7 10 20 30 40 50 60 70
• 5. example 2 public static void main(String[] args) { int[] listA = {11,22,36,42,15,46,27,48,19,10} int[] listB = new int[10]; int Total, Largest; // call sumArray method and return a value to Total Total = sumArray (listA, listA.length); System.out.println(“n The sum of ListA is :” + Total); // call indexLargestElement and return the indux value to Largest indLargest = indexLargestElement (listA, list.length); System.out.println(“n The largest element is :” + listA[Largest]); continue
• 6. public static int sumArray(int[] list, int noOfElements) { int index; int sum = 0; for (index = 0; index < noOfElement; index++) sum = sum + list[index]; return sum; } public static int indexLargestElement(int[] list, int noOfElement) { int index; int maxIndex = 0; for (index = 1; index < noOfElement; index++) if(list[maxIndex] < list[index]) maxIndex = index; return maxIndex; }
• 7. Array of String Objects String[] nameList = new String[5] nameList[0] = “Amanda Green”; nameList[1] = “Vijay Arora”; nameList[2] = “Sheila Mann”; nameList[3] = “Rohit Sharma”; nameList[4] = “Mandy Johnson”;
• 8. Array of Object  Can use arrays to manipulate objects.  Example: Create an array named array1 with N object of type T: T[] array1 = new T[N]  Can instantiate array1 as follows: for(int j=0; j < array1.length; j++) array1[j] = new T();  Eg: a) clock – hour, minute, second b) student – name, matric, age
• 9. example import java.util.*; public class ArrayOfObj { int N = 3; StudentInfo[] student = new StudentInfo[N]; public static void main (String[] args) { int N = 3; int i; ArrayOfObj arr = new ArrayOfObj(); StudentInfo[] Std = new StudentInfo[N]; Std = arr.InputData(); arr.PrintInfo(Std); } Input students information's (name,matric, age) into array and print out the output class StudentInfo{ String name; String matric; int age; }
• 10. public StudentInfo[] InputData() int i; StudentInfo[] student = new StudentInfo[N]; System.out.println("nEnter Students Information "); System.out.println("_______________________ ____ n"); for (i = 0; i< N; i++) { student[i] = new StudentInfo(); System.out.print("Name : "); student[i].name = input.readLine(); System.out.print("Matric No : "); student[i].matric = input.nextLine(); System.out.print("Age : "); student[i].age = input.nextInt(); System.out.println(); } return student; } public void PrintInfo(StudentInfo[] Std) { int i; System.out.println("List of students :n"); for (i=0;i<N;i++) { System.out.println((i+1) + ". " + Std[i].matric + " " + Std[i].name + " " + " " + Std[i].age); } }
• 11. Output Enter Students Information ___________________________ Name : BAHARUDIN OSMAN Matric No : S11111 Age : 30 Name : BADRUL HAZMI Matric No : S23212 Age : 28 Name : NUR BADRINA Matric No : S34213 Age : 27 List of students : 1. S11111 BAHARUDIN OSMAN 30 2. S23212 BADRUL HAZMI 28 3. S34213 NUR BADRINA 27
• 12. Statement below create an array of arrivalTimeEmp Clock[] arrivalTimeEmp = new Clock[100];
• 13. Instantiating of Array Objects for (int j = 0; j < arrivalTimeEmp.length; j++) arrivalTimeEmp[j] = new Clock();
• 14. Continue  Setting a time for index 49 arrivalTimeEmp[49].setTime(8, 5, 10);
• 15. Delete Object  Step i. Identify the element to delete ii. Point the object to delete null iii. Move up all elements (after deleted object) iv. Point the last element to null
• 16. for (i=0; i < student.length; i++) if(i==5) then student[i] = null null student Name Matric IC Name Matric IC Name Matric IC Step 1 : Identify the element to delete Step 2 : Point the object to delete to null - if the sixth element to delete
• 17. Step 3 : Move up all elements (after deleted object) Step 4 : Point the last element to null element A element B element C element D element E element element G element H element I element J [0] [1] [2] [3] [4] [5] [6] [7] [8] [9] element A element B element C element D element E element G element H element I element J [0] [1] [2] [3] [4] [5] [6] [7] [8] [9] for (i = 0; i < student.length; i++) if (i= =5) student[i] = student[student.length -1) if (i= = (student.length – 1)) student[i] = null Set the last element to null nullbefore studentstudent after