What do void methods return

I don't take a position on multiple exit points, but I will point out that leaving a function cleans up the local stack. KBoek 4, 4 4 gold badges 29 29 silver badges 45 45 bronze badges. Pesto Pesto MahdeTo MahdeTo This is great answer but I doubt beginners in java would really grasp what you're trying to say.

ElliotMok Fair enough. We all start out as beginners! Is this a good practice or doesn't matter whether we write return; or not? John Ellinwood John Ellinwood It exits the function and returns nothing. Something like return 1; would be incorrect since it returns integer 1. Albert Albert 3 3 gold badges 7 7 silver badges 16 16 bronze badges. Chris Ballance Chris Ballance GreyGoose 4 4 silver badges 12 12 bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook.

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Podcast Do polyglots have an edge when it comes to mastering programming Featured on Meta. Parameters and other variables only exist inside their own methods.

Inside main , there is no such thing as s. Similarly, inside printTwice there is no such thing as argument.

That variable belongs to main. Because variables only exist inside the methods where they are defined, they are often called local variables. But that format without the second int is only legal for variable declarations. In parameter lists, you need to specify the type of each variable separately. Pulling together the code fragments from the previous section, here is a complete class definition:.

And main has two variables, also named hour and minute. Although they have the same names, these variables are not the same.

Before the method is invoked, Java evaluates the arguments; in this example, the results are 12 and 0. Then it assigns those values to the parameters. Inside printTime , the value of hour is 12 , not 11 , and the value of minute is 0 , not Furthermore, if printTime modifies one of its parameters, that change has no effect on the variables in main.

One way to keep track of everything is to draw a stack diagram , which is a state diagram see Section 2.

The name of the method appears outside the frame; the variables and parameters appear inside. As with state diagrams, stack diagrams show variables and methods at a particular point in time. Figure 4. One of the nice things about Java is that it comes with an extensive library of classes and methods.

But before you use them, you might have to read the documentation. Documentation for other classes uses a similar format. The first line is the package that contains the class, such as java. The second line is the name of the class. The next section of the documentation is a narrative that explains the purpose of the class and includes examples of how to use it.

This text can be difficult to read because it uses terms we have not learned yet. But the examples are often very useful. A good way to get started with a new class is to paste the examples into a test file and see if you can compile and run them. One of the examples shows how you can use a Scanner to read input from a String instead of System.

The next line is a short description of what it does. It might take you some time to get comfortable reading documentation and learning which parts to ignore. And a little bit of documentation can save you a lot of debugging. A nice feature of the Java language is the ability to embed documentation in your source code.

That way, you can write it as you go, and as things change, it is easier to keep the documentation consistent with the code. If you include documentation in your source code, you can extract it automatically, and generate well-formatted HTML, using a tool called Javadoc. This tool is included in standard Java development environments, and it is widely used. In fact, the online documentation of the Java libraries is generated by Javadoc.

Anything in between is considered part of the documentation. The class comment explains the purpose of the class. The method comment explains what the method does. In general, inline comments are short phrases that help explain complex parts of a program. They are intended for other programmers reading and maintaining the source code. In contrast, Javadoc comments are longer, usually complete sentences. They explain what each method does, but they omit details about how the method works.

And they are intended for people who will use the methods without looking at the source code. Appropriate comments and documentation are essential for making source code readable. And remember that the person most likely to read your code in the future, and appreciate good documentation, is you.

The code for this chapter is in the ch04 directory of ThinkJavaCode. See page?? Before you start the exercises, we recommend that you compile and run the examples. If you have not already read Appendix A. It describes an efficient way to test programs that take input from the user and display specific output. The point of this exercise is to practice reading code and to make sure that you understand the flow of execution through a program with multiple methods.

Hint: Start by describing in words what ping and baffle do when they are invoked. Both value-returning functions and void functions receive values through their parameter lists. A value-returning function can only return one value to the calling environment.

The caller invokes calls a value-returning function by using its name and argument list in an expression i. Nor is it called from within an expression. Instead, the function call appears as a complete, stand-alone statement. Function Parameter Types: Two Types of Function Parameters: Value Parameter: formal parameter receives copy of content of corresponding actual parameter Reference Parameter: formal parameter receives location memory address of corresponding actual parameter Using Value and Reference Parameters: Value Parameters: Value of corresponding actual parameter copied into formal parameter Value parameter has own copy of data During program execution, value parameter manipulates data stored in own memory space Value parameters will accept expressions, constants, or variables from actual parameters i.

When a function is called: Memory for formal parameters in header and local variables declared in body of function allocated in function data area Value parameter : value of actual parameter copied into memory cell of its corresponding formal parameter Reference parameter : address of actual parameter passed to formal parameter content of formal parameter is an address During execution, changes made by formal parameter permanently change value of actual parameter Stream variables e.

Do nothing. Safer Pass by reference: Passes address of actual parameter Accesses original variable's contents via address Original variable's contents DO change How? By definition, a value-returning function returns a single value; this value is returned via the return statement. Use void functions with reference parameters to return modify more than one value.

Use pass-by-const-reference to pass large objects that do NOT need to be modified Return result rather than modify object through reference argument value-returning function Use pass-by-reference ONLY when necessary. What is scope?

As a rule, functions should not contain any identifier with same name as global variable. Syntax for declaring external variable: extern int var; A global variable, that is a variable declared outside of all functions in a file, is accessible by any code in that file. By declaring extern variables, for programs that require multiple files, variables declared in one file can be accessible in other files.