Method Calling Mechanisms in Java.

In this article,Method Calling Mechanisms in Java is explained in detail with an example.
Based on nature of arguments used to call a user defined method in java, we have two types of method calling mechanisms.They are

• Call by value.
• Call by reference.

Call by Value

In this mechanism, we pass a copy of actual arguments to call a user-defined method and formal parameters are also of same data type.

Any changes done with formal parameters are NOT reflected to actual arguments.

Ex

//program related to Method Calling Mechanisms in Java--call by value.

class CallByValue

{

public static void main(String args[])

{

Test obj=new Test();

int a=50,b=60;

System.out.println("Values of A and B before call: "+a+" "+b);

obj.meth(a,b); //actual arguments..

System.out.println("Values of A and B after call: "+a+" "+b);

}

}

class test

{

void main(int i,int j) //i,j are formal parameters.

{

i*=2;

j/=2;

System.out.println("Values of I and J are: "+i+" "+j);

}

}

Output
Values of A and B before call: 50 60
Values of I and J are: 100 30
Values of A and B after call: 50 60

                            To get the code file use me.

Call by reference.

In java,We don't have the concept of pointers, but still, this mechanism is done through"object reference-variables". (From topic Method Calling Mechanisms in Java)

Ex

A obj=new A();

diagram

In this Mechanism, we pass object-reference-variables as the actual argument to call a user defined method and formal parameters are also object-reference variables of same class type. Any change done with formal-parameters is directly reflected to the actual argument.

Ex

//program related to Method Calling Mechanisms in Java--call by reference.

class A

{

int a,b;

A(int i,int j)

{

a=i;

b=j;

}

void method1(A obj1) //object reference of class A

{

obj1.a*=2;

obj1.b*=2;

}

}

class CallByReference

{

public static void main(String args[])

{

A obj=new A(10,20);

System.out.println("A and B before call is: "+obj.a+" "+obj.b);

obj.method1(obj);

System.out.println("A and B After call is: "+obj.a+" "+obj.b);

}

}

Output
A and B before call is: 10 20
A and B After call is: 20 40

                            To get the code file use me.

Continue to next topic Access Modifiers in Java.

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