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191 Lessons1. Introduction to Java
2. What is Java?
3. History of Java
4. Java Tutorial for Beginners
5. How Do Java Programs Work?
6. JDK in Java
7. C++ Vs Java
8. Java vs. Python
9. Java vs. JavaScript
10. From Java Source Code to Executable
11. How to Install Java in Linux
12. How to Install Java in Windows 10
13. Java Hello World Program
14. Structure of Java Program and Java Syntax
15. Operators in Java
16. Java If-else
17. Switch Case In Java
18. Loops in Java
19. Infinite loop in Java
20. For Loop in Java
21. For Each Loop in Java
22. Constructor in Java
23. Constructor Overloading in Java
24. Copy Constructor in Java
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25. Default Constructor in Java
26. Parameterized Constructors in Java
27. Constructor Chaining In Java
28. Finalize Method in Java
29. Static Method in Java
30. Equals Method in Java
31. Abstract Method in Java
32. toString() Method in Java
33. Difference between equals method in Java
34. Inheritance in Java
35. Multiple Inheritance in Java
36. Hierarchical Inheritance in Java
37. Java Classes and Objects
38. Scanner Class in java
39. All classes in java are inherited from which class
40. What is Nested Class in Java
41. POJO Class in Java
42. Anonymous Class in Java
43. Final Class in Java
44. Object Class in Java
45. Packages in Java
46. Access Modifiers in Java
47. Static Keyword In Java
48. Final Keyword in Java
49. Checked and Unchecked Exceptions in Java
50. User Defined Exception in Java
51. Error vs. Exception in Java
52. Java Collection
53. Collections in Java
54. Garbage Collection in Java
55. Generics In Java
56. Java Interfaces
57. Functional Interface in Java
58. Marker Interface in Java
59. Streams in Java
60. Byte stream in java
61. File Handling in Java
62. Thread in Java
63. Thread Lifecycle In Java
64. Daemon Thread in Java
65. Thread Priority in Java
66. Deadlock in Java
67. String Pool in Java
68. Java Database Connectivity(JDBC)
69. Design Patterns in Java
70. Functional Programming in Java
71. OOP vs Functional vs Procedural
72. Heap Memory and Stack Memory in Java
73. Applet in Java
74. Java Swing
75. Java Frameworks
76. Hibernate Framework
77. JUnit Testing
78. How to Install Eclipse IDE for Java?
79. Command line arguments in Java
80. Jar file in Java
81. Java Clean Code
82. OOPs Concepts in Java
83. Java OOPs Concepts
84. Overloading vs Overriding in Java
85. Java 8 features
86. String in Java
87. String to int in Java
88. Why String Is Immutable in Java?
89. Primitive Data Types in Java
90. Non-Primitive Data Types in Java
91. This and Super Keyword in Java
92. HashMap in Java
93. Comparable And Comparator in Java
94. Type Casting in Java
95. Arrays Sort in Java with Examples
96. Variable Hiding and Variable Shadowing in Java
97. Enum in Java
98. Substring in Java
99. Pattern Programs in Java
100. Hashcode in Java
101. What is ByteCode in Java?
102. How To Take Input From User in Java
103. GCD of Two Numbers in Java
104. Linked List in Java
105. Arithmetic Operators in Java
106. Conditional Operators in Java
107. Stack and Queue in Java
108. Array Length in Java
109. Number Pattern Program in Java
110. Split in java
111. Map In Java
112. Difference Between Throw and Throws in Java
113. Difference Between Data Hiding and Abstraction
114. HashSet in Java
115. String Length in Java
116. Factorial Using Recursion in Java
117. DateFormat in Java
118. StringBuilder Class in java
119. Instance variables in Java
120. Java List Size
121. Java APIs
122. Reverse an Array in Java
123. StringBuffer and StringBuilder Difference in Java
124. Java Program to Add Two Numbers
125. String to Array in Java
126. Regular Expressions in Java
127. Identifiers in Java
128. Data Structures in Java
129. Set in Java
130. Pass By Value and Call By Reference in Java
131. Try Catch in Java
132. Bubble Sort in Java
133. Caesar Cipher Program in Java
134. Queue in Java
135. Object Creation in Java
136. Multidimensional Array in Java
137. How to Read a File in Java
138. String Comparison in Java
139. Volatile Keyword in Java
140. Control Statements in Java
141. Jagged Array in Java
142. Two-Dimensional Array in Java
143. Java String Format
144. Replace in Java
145. charAt() in Java
146. CompareTo in Java
147. Matrix Multiplication in Java
148. Static Variable in Java
149. Event Handling in Java
150. parseInt in Java
151. Java ArrayList forEach
152. Abstraction in Java
153. String Input in Java
154. Logical Operators in Java
155. instanceof in Java
156. Math Floor in Java
157. Selection Sort Java
158. int to char in Java
159. Stringtokenizer in java
160. Implementing and Manipulating Abs in Java
161. Char array to string in java
162. Convert Double To String In Java
163. Deque in Java
164. Converting a List to an Array in Java
165. The Max function in java
166. Removing whitespace from string in java
167. String arrays in Java
168. Strings in Java Vs Strings in Cpp
169. Sum of digits of a number in Java
170. Art of Graphical User Interfaces
171. Trim in Java
172. RxJava
173. Recursion in Java
174. HashSet Java
175. Difference Between Java and Python
176. Square Root in Java
177. Reverse A String in Java
178. Even Odd Program in Java
179. Fibonacci Series in Java
180. Prime Number Program in Java
181. Java Program to Print Prime Numbers in a Given Range
182. Java Leap Year Program
183. Swapping of Two Numbers in Java
184. LCM of Two Numbers in Java
185. Math.sqrt() Function in Java
186. Area of Triangle in Java
187. Sort a String In Java
188. Factorial Program in Java
189. Javafx
190. Lambda expression in java
191. Setup Java Home and IDE on macOS
Do you want to be proficient in Java? Read this tutorial to master copy constructor, a vital concept in Java. This tutorial covers the advantages of copy constructors, copy constructor vs. clone() method, writing a copy constructor, and creating duplicate objects without a copy constructor.
Copy constructors in Java are special constructors. They allow the creation of a new object by copying the values of an already present object of the same class. You can create an exact duplicate of an object by deploying copy constructors.
The copy constructor has the same name as the class. For instance, if the class name is upGrad, the copy constructor will also be named upGrad. The copy constructor does not have a return type, not even void. It is responsible for creating a new object, so it doesn't return anything explicitly.
For example, for the class upGrad:
public class upGrad {
public upGrad(upGrad object) {
// Copy the values from the provided object to create a new object
// Assign the field values of 'object' to the corresponding fields of 'this' object
}
// Other constructors and methods of the class
}
The copy constructor takes a single parameter of the same class type as the one being constructed. This parameter represents the object from which the values are to be copied. In the example syntax, the parameter is named object and has the type upGrad.
The access specifier of the copy constructor is typically set to the same as the class's other constructors and methods. It determines the visibility and accessibility of the constructor from other parts of the code. In the above example, the copy constructor is declared with the default access specifier (public), which means it is accessible within the same package.
In the example above, upGrad is a class with two fields: field1 of type int and field2 of type String. The copy constructor takes an object of the same class (upGrad) as a parameter named object.
Inside the copy constructor, the values of field1 and field2 are copied from the provided object to the new object created using the this reference. This way, when you create a new instance of upGrad using the copy constructor, the values of field1 and field2 will be identical to those of the object you passed as an argument.
Now that you know how to use a copy constructor let us look at a working program:
public class upGradTutorials {
private int value;
// Constructor
public upGradTutorials(int value) {
this.value = value;
}
// Copy constructor
public upGradTutorials(upGradTutorials other) {
this.value = other.value;
}
public int getValue() {
return value;
}
public void setValue(int value) {
this.value = value;
}
public static void main(String[] args) {
upGradTutorials obj1 = new upGradTutorials(10);
upGradTutorials obj2 = new upGradTutorials(obj1); // Using the copy constructor
System.out.println(obj1.getValue()); // Output: 10
System.out.println(obj2.getValue()); // Output: 10
obj1.setValue(20);
System.out.println(obj1.getValue()); // Output: 20
System.out.println(obj2.getValue()); // Output: 10
}
}
In the above example, we create two instances of the upGradTutorials class: obj1 and obj2 in the main method. obj1 is initialized with a value of 10 using the constructor, and obj2 is created using the copy constructor, passing obj1 as an argument.
We then print the values of obj1 and obj2, which initially show 10 for both. After that, we change the value of obj1 to 20 using the setValue method. When we print the values again, we can see that the change in obj1 does not affect obj2, demonstrating the behavior of a copy constructor.
Using a copy constructor in Java offers several advantages that can greatly benefit programmers in code implementation.
First, a copy constructor reduces complexities when dealing with objects that have multiple parameters. The copy constructor provides a concise and convenient way to create a new object. This is done instead of passing each parameter individually. It is done by merely providing an existing object as the parameter. As a result, this simplifies the code.
Second, a copy constructor simplifies updating the constructor when a new field is added to the class. Only the input parameter must be updated in the constructor to include the new field, rather than modifying every instance where the constructor is called throughout the codebase. This reduces the chances of introducing errors. It also saves time during maintenance.
Also, using a copy constructor makes the need for typecasting redundant. The copy constructor creates a new object of a similar class. Hence, there is no requirement to cast the object explicitly. This enhances code clarity. It also minimizes the risk of type-related errors.
Finally, a copy constructor allows modification of fields declared as final. As we know, regular constructors cannot modify final fields once they are initialized. However, a copy constructor can overwrite these fields during object creation. This can be useful when creating a new object with similar values but with some alterations.
We can create duplicate objects in Java without using a copy constructor by utilizing other techniques, such as implementing the Cloneable interface and overriding the clone() method.
Here is an example:
In the above program, the upGradTutorials class implements the Cloneable interface, indicating that class instances can be cloned. The class also overrides the clone() method inherited from Object to enable cloning.
Inside the main method, we create an instance of upGradTutorials named obj1 with an initial value of 10. We then attempt to clone obj1 using the clone() method and assign the cloned object to obj2.
We print the values of obj1 and obj2, which initially show 10 for both. After that, we modify the value of obj1 to 20 using the setValue method. When we print the values again, we will observe that the change in obj1 does not affect obj2 (similar to the operation of a copy constructor), indicating that the cloning operation created a separate object.
In Java, there is no default copy constructor provided by the language itself. However, the compiler automatically generates a default copy constructor if we do not define any constructor in your class. This default copy constructor performs a shallow copy of the object's fields, meaning it copies the field references rather than creating new objects.
Here is an example:
public class upGradTutorials {
private int value;
private String name;
public int getValue() {
return value;
}
public void setValue(int value) {
this.value = value;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public static void main(String[] args) {
upGradTutorials obj1 = new upGradTutorials();
obj1.setValue(10);
obj1.setName("Aritra");
upGradTutorials obj2 = new upGradTutorials();
obj2 = obj1; // Performing a shallow copy
System.out.println(obj1.getValue()); // Output: 10
System.out.println(obj1.getName()); // Output: Aritra
System.out.println(obj2.getValue()); // Output: 10
System.out.println(obj2.getName()); // Output: Aritra
obj1.setValue(20);
obj1.setName("Manisha");
System.out.println(obj1.getValue()); // Output: 20
System.out.println(obj1.getName()); // Output: Manisha
System.out.println(obj2.getValue()); // Output: 20 (same as obj1)
System.out.println(obj2.getName()); // Output: Manisha (same as obj1)
}
}
To create a deep copy constructor in Java, you need to manually copy each field of the object, ensuring that new instances of any mutable objects are created.
Here is an example:
public class Person {
private String name;
public Person(String name) {
this.name = name;
}
public Person(Person other) {
this.name = other.name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public static void main(String[] args) {
Person person1 = new Person("Atriya");
Person person2 = new Person(person1); // Using the deep copy constructor
System.out.println(person1.getName()); // Output: Atriya
System.out.println(person2.getName()); // Output: Atriya
person1.setName("Aritra");
System.out.println(person1.getName()); // Output: Aritra
System.out.println(person2.getName()); // Output: Atriya (unchanged)
}
}
In this example, we have a Person class with a single name field. The class has a deep copy constructor that copies the value of the name field.
Inside the main method, we create a Person object person1 with an initial name. Then, we create another Person object, person2, by using the deep copy constructor, ensuring a new instance is created with the same name value.
We print the values of person1 and person2, which initially show the same name value.
Feature | Copy Constructor | clone() Method |
Definition | A special constructor that creates a new object. This is done by copying values from an existing object of the same class. | It is a method defined in the Cloneable interface. It creates a new object by copying the fields of an existing object. |
Availability | Depends on whether the programmer defines and implements it. | Available for classes that implement the Cloneable interface. |
Accessibility | Can be accessed from any class within the same package or subclass. | Needs to be called using the clone() method and may require casting. |
Object Creation | Creates a new object of the same class with copied values. | Creates a new object by copying fields, typically using a shallow copy. |
Required Interface | No specific interface is required. | The class must implement the Cloneable interface. |
Field Accessibility | Can access all fields, including private fields. | Can only access public and protected fields, requiring additional steps for private fields. |
Copying Behavior | Provides control over how fields are copied, allowing customization during object creation. | Copies fields using a shallow copy by default, requiring additional steps for deep copy. |
Exceptions | Can throw exceptions as per the defined logic. | Requires handling of checked exceptions (CloneNotSupportedException). |
Usage Flexibility | Offers flexibility in terms of customization and handling complex copying scenarios. | Provides less flexibility compared to copy constructors. |
Inheritance and Polymorphism | Copy constructors are not inherited. They need to be explicitly defined in each subclass. | clone() method is inherited. They can be overridden in subclasses for customized behavior. |
It is to be that copy constructor provides more flexibility and control over the object creation process. However, the clone() method provides a standardized approach for creating copies of objects.
Using a copy constructor is often a simpler and more readable approach. This is especially if you have control over the class and its implementation. Conversely, using the clone() method can be a suitable choice if you work with classes that already implement Cloneable and need to adhere to existing cloning conventions.
A copy constructor is essential in several circumstances where you would want to create a new object that is a copy of an existing object. If you wish to master concepts such as copy constructors in Java, seeking professional training is recommended. A certified course in Java can have several career benefits. Learning platforms such as upGrad have several courses in computer science that can help you master programming languages faster and establish a bright career as a professional.
1. Is a copy constructor the same as a regular constructor?
A copy constructor creates a new object by copying the values of an already present object. A regular constructor initializes a new object with initial values. Copy constructors are typically used for object duplication or cloning. Regular constructors are used for general object creation.
2. Can I create a deep copy using a copy constructor in Java?
By default, copy constructors in Java create a shallow copy. This means that the references to other objects are copied. But the objects themselves are not copied. To create a deep copy, you must explicitly handle the deep copying logic within the copy constructor.
3. Can a copy constructor be inherited by subclasses?
Subclasses do not inherit copy constructors. Still, a subclass can have a copy constructor. For this, it must define its own copy constructor explicitly. Each class in the inheritance hierarchy must implement its own copy constructor. This is the case if object copying behavior is required.
PAVAN VADAPALLI
Director of Engineering
Director of Engineering @ upGrad. Motivated to leverage technology to solve problems. Seasoned leader for startups and fast moving orgs. Working …Read More
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upGrad does not grant credit; credits are granted, accepted or transferred at the sole discretion of the relevant educational institution offering the diploma or degree. We advise you to enquire further regarding the suitability of this program for your academic, professional requirements and job prospects before enr...