The author of this post
has written many articles about Java web development. In this article, he will
share some important facts about Pass by Value and Pass by Reference. You can
learn a lot more about these methods- just understand the details shared by the
author in this post.
• In
basic, there are two methods that a computer language can pass an argument to a
subroutine. 1) Pass-By-Value and 2) Pass-By-Reference
• In
Java, Objects are passed by reference, and primaries are passed by value.
• All
of us can simply agree that primaries are passed by value; there’s no such
thing in Java as a pointer to a primary.
• Java
uses the pass-by-value. There is no pass-by-reference in Java. This Java
tutorial is to walk you via the difference between pass by value and pass by
reference, then search how Java uses pass by value with samples. Some say that
in Java primaries are passed by value and objects are passed by reference. It
is not right.
• But,
Objects are not passed by reference. A true statement would be Object
references are passed by value.
• Java
does manage objects by reference, and all object variables are references. But,
Java doesn’t pass method arguments by reference; it passes them by value.
Pass by Value
• Real parameter expressions that are
passed to a method are estimate and a value is derived. Then this value is
stored in a location and then it becomes the formal parameter to the call on
method. This structure is called pass-by-value. Not the real reference but Passing
a copy of the value.
• In Java, when you pass a primary type
to a method, it is passed by value. So, what happens to the parameter that
receives the argument has no effect outside the method.
EXAMPLE OF PASS BY VALUE
public class Example1
{
public static void main(String
args[]) {
int number
= 3;
nextPrint(number);
System.out.println(“Print number Inside main(): ” + number);
}
public static void nextPrint(int number)
{
number++;
System.out.println(“Print number Inside nextPrint(): ” +
number);
}
}
Output :
Print
number Inside nextPrint(): 4
Print
number Inside main(): 3
Above
example, Primitives are passed as pass by values to method parameters and
Java
Pass by reference both main() method and nextPrint() method should have printed
the same value.
Pass by
Reference
1. By name or reference to the real
parameter is passed to the method, so that it’s called pass by reference.
Passing the address of the object, so that you may examine the real object.
2. Java is always Pass by Value and not
pass by reference.
3. When you pass an object to a method,
the condition changes badly, because objects are passed by successful
call-by-reference.
4. When you generate a variable of a class
type, you are only creating a reference to an object.
5. When you pass this reference to a
method, the parameter that gets it will refer to the same object as that referred
to by the argument. These successful means that object are passed to methods by
use of call-by-reference.
EXAMPLE OF PASS BY REFERENCE.
public class Example2
{
public static void main(String
args[]) {
Car car1 = new Car(“Rolls-Royce”);
Car car2 = new Car(“BMW”);
System.out.println(“Brand
of Car Inside main() before: 1) “+ car1.brand + ” 2) ” + car2.brand);
brandPrint(car1, car2);
System.out.println(“Brand
of Car Inside main() after: 1) “+ car1.brand + ” 2) ” + car2.brand);
swap(car1, car2);
System.out.println(“Brand
of Car after swap: 1) “+ car1.brand + ” 2)” + car2.brand);
}
public static void brandPrint(Car
car1, Car car2){
car1.brand = “Bugatti”;
car2.brand = “Ferrari”;
}
public static void swap(Car
c1, Car c2){
Car temp = new Car(“”);
temp = c1;
c1 = c2;
c2 = temp;
}
private static class Car{
private String
brand;
public Car(String
brand){
this.brand
= brand;
}
}
}
Output:
Brand of Car Inside main() before: Rolls-Royce
Brand of Car Inside brandPrint():
Bugatti
Brand of Car Inside main() after: Bugatti
1. Above
example, change made in method parameter is reflected globally. The brands of
cars are changed in all places, which means one object is used in both methods.
Swap() method test may be used for Pass by reference.
2. You
will find that method swap() within from the main() method is passed two
objects car1 and car2 those are received by swap() in c1and c2 references
respectively. Next inner swap() method c1 and c2 are exchanged. By doing so c1
holds the object earlier referred to by c2 and c2 does the opposite. In this procedure
of exchanging formal parameters c1 and c2 there would be no impact on car1 and
car2, which states that in Java arguments are passed by value, not by
reference.
3. That’s
how Java handles pass-by-value and pass-by-reference mechanisms of passing
parameters to methods.
4. Objects
are not swapped because Java uses the pass-by values.
5. Key
point to mention is that “The reference is copied as a value” to a new variable
and it is given as a formal parameter to the called method.
6. If
you pass an object as a method parameter in Java it passes “value of reference”
or object reference or handles to Object in Java. Here reference expression is fully
different from the reference expression used in C and C+ which directly points
to the memory address of the variable and is subject to pointer arithmetic. In
Java object can only be accessed by its reference as you can’t get the memory
address where the object is stored or more precisely there is no method to get
the value of an object by passing the memory address.
The author of this post is a java web development professional. He has good exposure to java app development
and has built many apps for distinct businesses. If you have any question
related to Pass by Value and Pass by reference, then comment on this post. The
experts will answer your query and will share proper thoughts about the
subject.
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