Java：子例程和方法有什么区别？

Question

What is the difference?

public write(){
// dostuff
}

Is the code above a subroutine, a method, or a program block?

I don't understand these terms because the meaning of them are all so similar?

So, if I was being very strict and pedantic, then which one would it be? I prefer calling them subroutines, is this STRICTLY correct?

Programming language: JAVA

EDIT: Thanks, I understand now but what would be the safest way to call it? Block? I use multiple programming languages, would the term "block" suffice?

Can I call a function a block?

So can I refer everything as a block? It will be easier for me, right?

I won't call a block a function or subroutine, but I will call a function, methods and whatever as a block. Would that be fine, calling them as a block?

So, does this mean this is somewhat ACCURATE? A local variable is not accessed outside of the program block (yes, there are a few circumstances that this is not true).

Answer 1

1. A subroutine is something you can call that returns to you.
2. A function is a subroutine that returns aa value.
3. A method is a subroutine or function that you can call on an object in an OO language.

Answer 2

None of the above, because it doesn't have a return value. It's only "correct" if it's a no-argument constructor for a class named write, in a file named write.java. And even that violates the Sun Java coding standards.

Subroutine is a term from functional/procedural languages like FORTRAN and COBOL. Those languages keep data and methods separate, with methods operating on the data they are given.

Objects encapsulate data and methods into instances. Most object-oriented programmers would prefer method. Your "preference" for subroutine will mark you as quaint and out of step.

I don't hear "subroutine" much anymore. I'd get used to "method" if I were you.

Answer 3

In the first place, what you have there is a constructor, and not a method, a proper method returning void(nothing) would be one like this(according to C# or Java syntax):

public void write()
{}

Now, regarding to what you initially asked: What's the difference between subroutine and method ?, Well, there is basically none. But if you want to go deeper, then we'll have to go to assembly programming IMO. Subroutines in assembly, are in fact different from methods in two things:

1. They don't get parameters passed
2. They don't return anything

And, you probably are asking yourself: Then how do I process anything at all, how this subroutine works? In assembly, here is where registers do their role, instead of passing a parameter to your subroutine, like you do with methods in every high level programming language, you have to save the value(parameter) you are going process before calling the subroutine, making sure that this value won't get affected before you reach the subroutine. In the same fashion, you'll keep the resulting value in another register for using it later. There are other ways to do this in assembly, commonly used too, by using the stack pushing and popping values from it, but I think I made my point clear enough. If serves for anything at all, I'll post you a piece o code in assembly using a simple subroutine to add two numbers:

org 00H

mov R3,#10                 ;save the first parameter
mov R4,#20                 ;save the second parameter

call Sum                   ;execute the subroutine

mov A,R3                   ;mov 30 to accumulator

Sum:                       ;subroutine declaration
add R3,R4
ret

end