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Explain the passing parameters as function in Call by Value and Call by Reference and then distinguish between them?
Call by value essentially passes a copy of an object's value whereas call by reference essentially passes the object itself. Pass by reference is the preferred method whenever possible as call by value will automatically invoke the object's copy constructor, which is often unnecessary, especially if the object is not affected by the function call (pass by constant reference).
When does this pointer get created?
When we call non static method with respect to class object then this pointer is created which keep the reference of that object.
Static method can be call object?
yes we can call a static method with object
Can you pass object as an argument to a method?
if you have a function or a method that takes Object as a parameter, you can call that function or method and pass an Object as follows: Let's say you have a class that extends Object and a function as follows public class A extends Object { ..... } void function ( A arg ){ ..... } To call this function, you need an instance of the class A A objectInstance = new A(); function(objectInstance); The next line shows how to pass an instance of the class A to the function.
Can the parameter of the copy constructor be passed by value?
No. The parameter of the copy constructor is always passed by reference, specifically, a const reference to the class.Think about it. If it were passed by value, then the compiler would already know how to copy the object into the formal parameter, but the purpose of the copy constructor is to provide the code to copy the object, so its kind of a "cart before the horse" thing to think about call by value here.
Explain the passing parameters as function in Call by Value and Call by Reference and then distinguish between them?
Call by value essentially passes a copy of an object's value whereas call by reference essentially passes the object itself. Pass by reference is the preferred method whenever possible as call by value will automatically invoke the object's copy constructor, which is often unnecessary, especially if the object is not affected by the function call (pass by constant reference).
When does this pointer get created?
When we call non static method with respect to class object then this pointer is created which keep the reference of that object.
Call by ref are passing object?
yeah.... in call by reference, the real object is passed and whatever are the changes done to that object, they are reflected even on returning back from the function. so actual values are passed rather than the copy of them as in case of call by value.
Static method can be call object?
yes we can call a static method with object
What is a call by reference?
In C++ (C Plus Plus), when you call by reference, you are directly accessing the data of the referenced object. When you pass an object to a function by reference, any and all alterations to the object made within the function carry through to the actual object.
Can you pass object as an argument to a method?
if you have a function or a method that takes Object as a parameter, you can call that function or method and pass an Object as follows: Let's say you have a class that extends Object and a function as follows public class A extends Object { ..... } void function ( A arg ){ ..... } To call this function, you need an instance of the class A A objectInstance = new A(); function(objectInstance); The next line shows how to pass an instance of the class A to the function.
Do functions get called by reference only?
No. Function parameters are passed by value. Always. Even the so called "call by reference" is a value - the value of the pointer or the address of the object - but what is placed in the parameter list is a value.
Can the parameter of the copy constructor be passed by value?
No. The parameter of the copy constructor is always passed by reference, specifically, a const reference to the class.Think about it. If it were passed by value, then the compiler would already know how to copy the object into the formal parameter, but the purpose of the copy constructor is to provide the code to copy the object, so its kind of a "cart before the horse" thing to think about call by value here.
Why not sending arefrence to copy constructor will cause an infinite loop?
A copy constructor gets called any time an object needs to be copied. Unlike in some of the newer languages like Java, you can chose to pass objects either by reference or by value. When you pass by reference, only the address of the function is copied. However, if you pass by value, the whole object must be copied. In order to copy the object, the copy constructor will get called. If the copy constructor's parameter is not a reference, then the object will get passed by value. When the object gets passed by value, it needs to get copied so it will call the same copy constructor. Because the object is still being passed by value it'll call itself again to create a copy of itself. The copy constructor will continue to call itself until the stack overflows.
Can main method be non-static?
No, the reason is simple: A method marked as a static means, that you don't need create an instance (create an object with the 'new' operator) in order to use it. The main method is the entry point for a java application, therefor there is nothing after you call it. no one who can create an object of the type of your class and call the main method. So the jvm must call the main method with no object reference.
What is calling by reference?
In C++ (C Plus Plus), when you call by reference, you are directly accessing the data of the referenced object. When you pass an object to a function by reference, any and all alterations to the object made within the function carry through to the actual object.
Why you pass something by reference and then make it const while call by reference mean you want to change it?
Call by reference does not necessarily mean you want to change something. It simply means that you are passing a pointer to the object rather than the object itself. This can be cost effective if the object is large, in comparison to a pointer. Making the call by reference const is an effective tool for doing this when you do not intend to modify the object, and you want to make sure you don't accidentally do so.
