Chapter2 array of objects
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This document discusses arrays of objects in object-oriented programming. It outlines that a class can be used as a new data type, and arrays can be defined to hold multiple objects of that class. Methods can be used to manage arrays of objects, such as adding, deleting, and searching for objects. The document also explains that objects are passed by reference to methods rather than by value. An immutable class is defined as one that does not allow changes to its private data fields once an object is created. The document provides a full example of a contact book program that uses a Contact class and ManagArray class to store contact objects in an array and perform operations on them.
![Array of User defined type
int sal;
int id;
String name;
…
Employee class
e1
e2
e3
e4
e5
e6
e7
e8
Employee [ ] x ;](https://image.slidesharecdn.com/chapter2arrayofobjects-160404212756/85/Chapter2-array-of-objects-6-320.jpg)
![Array of User defined type
o An array of objects is actually an array of reference variables.
Circle[] circleArray = new Circle[10];](https://image.slidesharecdn.com/chapter2arrayofobjects-160404212756/85/Chapter2-array-of-objects-7-320.jpg)
![Array of User defined type
Class [ ] x ;
Add objects
Delete objects
Looking for objects
Printing all data
….
Class
To management many objects
which are stored in array](https://image.slidesharecdn.com/chapter2arrayofobjects-160404212756/85/Chapter2-array-of-objects-8-320.jpg)
![Example: ContactBook
int serial;
String name;
String mobile;
String address;
…
Contact class
int count;
void search(){}
void print(){}
void insert(){}
…
ManagArray class
e1
e2
e3
e4
e5
e6
e7
e8
Contact [ ] conArray ;](https://image.slidesharecdn.com/chapter2arrayofobjects-160404212756/85/Chapter2-array-of-objects-13-320.jpg)
![Contact book
class Contact {
private String name;
//….
public Contact (String name, String mobile) { … }
}
class ManagArray {
private Contact [ ] contBook;
private int count;
// …
public ManagArray(int size){ … }
public void insert(Contact c) { …. }
public void printData() { … }
public void searchByName(String name) { … }
}](https://image.slidesharecdn.com/chapter2arrayofobjects-160404212756/85/Chapter2-array-of-objects-14-320.jpg)
Chapter2 array of objects
- 1. Object Oriented Programming Chapter 2: Array of objects Prepared by: Mahmoud Rafeek Alfarra 2016
- 3. Outlines ◉ User defined type ◉ Array of User defined type (new class) ◉ Passing Objects to Methods ◉ Immutable Objects and Classes ◉ Full Example Note: I have prepared this material Based on (Liang: “Introduction to Programming using Java”, 10’th edition, 2015)
- 4. Lecture Let’s think on fieldes of class 3
- 5. o As the defined class is a new data type, we can defined any variables or arrays of it. User defined type
- 6. Array of User defined type int sal; int id; String name; … Employee class e1 e2 e3 e4 e5 e6 e7 e8 Employee [ ] x ;
- 7. Array of User defined type o An array of objects is actually an array of reference variables. Circle[] circleArray = new Circle[10];
- 8. Array of User defined type Class [ ] x ; Add objects Delete objects Looking for objects Printing all data …. Class To management many objects which are stored in array
- 9. o Passing by value for primitive type value (the value is passed to the parameter) o Passing by value for reference type value (the value is the reference to the object) Passing Objects to Methods
- 10. Passing Objects to Methods
- 11. o For a class to be immutable, it must mark all data fields private and provide no mutator methods and no accessor methods that would return a reference to a mutable data field object. o If the contents of an object cannot be changed once the object is created, the object is called an immutable object and its class is called an immutable class. Immutable Objects and Classes
- 12. Immutable ? public class Student { private int id; private BirthDate birthDate; public Student(int ssn, int year, int month, int day) { id = ssn; birthDate = new BirthDate(year, month, day); } public int getId() { return id; } public BirthDate getBirthDate() { return birthDate; } } public class BirthDate { private int year; private int month; private int day; public BirthDate(int newYear, int newMonth, int newDay) { year = newYear; month = newMonth; day = newDay; } public void setYear(int newYear) { year = newYear; } }
- 13. Example: ContactBook int serial; String name; String mobile; String address; … Contact class int count; void search(){} void print(){} void insert(){} … ManagArray class e1 e2 e3 e4 e5 e6 e7 e8 Contact [ ] conArray ;
- 14. Contact book class Contact { private String name; //…. public Contact (String name, String mobile) { … } } class ManagArray { private Contact [ ] contBook; private int count; // … public ManagArray(int size){ … } public void insert(Contact c) { …. } public void printData() { … } public void searchByName(String name) { … } }
- 15. static int x; class Test obj1 X = 0X = 1 obj2 X = 2 obj3 X = 3 Now: Print Obj1.X 3 Print Obj1.X 3 Print Obj1.X 3
- 16. Practices Group 1 Give 3 examples to array of objects. Group 2 Diffrenciate between Passing by value and by reference. Group 3 Develop Immutable class.
- 17. THANKS! Any questions? You can find me at: Fb/mahmoudRAlfarra Staff.cst.ps/mfarra Youtube.com/mralfarra1 @mralfarra