2.7 Jb0130: java oop: a gentle introduction to methods in java  (Page 4/5)

Calling the sqrt method

I'm not sure why you would want to do this, but the code fragment in Listing 2

• calls the sqrt method and
• passes a copy of the value stored in the beans variable as a parameter.

The sqrt method calculates and returns the square root of the number that it receives as its incoming parameter. In this case, it returns the square root of the price of a can of beans.

A place to save the square root

I needed some place to save the square root value until I could display it on the computer screen later in the program. I declared another variable named sqRtBns in the code fragment in Listing 2 . I also caused the value returned from the sqrt method to be stored in, or assigned to, this new variable named sqRtBns .

How should we interpret this code fragment?

You can think of the process implemented by the code fragment in Listing 2 as follows.

First note that there is an equal sign (=) near the center of the line of code. (Later we will learn that this is called the assignment operator.)

The code on the left-hand side of the assignment operator causes a new chunk of memory to be set aside and named sqRtBns . (We call this chunk of code a variable.)

The code on the right-hand side of the assignment operator calls the sqrt method, passing a copy of the value stored in the beans variable to the method.

When the sqrt method returns the value that is the square root of its incoming parameter, the assignment operator causes that value to be stored and saved in (assigned to) the variable named sqRtBns .

Now display the square root value

The code in the fragment in Listing 3 causes the value now stored in sqRtBns to be displayed on the computer screen.

Another method is called here

The display of the square root value is accomplished by

• calling another standard method named println and
• passing a copy of the value stored in sqRtBns as a parameter to the method.

The println method performs an action (displaying something on the computer screen) and doesn't return a value.

A method exhibits behavior

We say that a method exhibits behavior. The behavior of the sqrt method is to calculate and return the square root of the value passed to it as a parameter.

The behavior of the println method is to cause its incoming parameter to be displayed on the computer screen.

What do we mean by syntax?

Syntax is a word that is often used in computer programming. The thesaurus in the editor that I am using to type this document says that asynonym for syntax is grammar.

I also like to think of syntax as meaning something very similar to format.

Syntax for passing parameters

Note the syntax in Listing 2 and Listing 3 for passing a parameter to the method. The syntax consists of following the name of the method with a pair of matching parentheses that contain the parameter. If more than one parameter is being passed, they are all included within the parentheses and separated by commas.Usually, the order of the parameters is important if more than one parameter is being passed.