Java Reference
In-Depth Information
ple, we write a method printSums , which contains two calls to method
printSum . Class PrintExample , with all three methods discussed in this section,
appears in Fig. 2.1.
Method printSums go inside class PrintExample . Because printSum and
printSums are defined in the same class, procedure printSums can call
printSum without having to write PrintExample.printSum(...); .
At times, you may want to execute parts of a program by hand. In doing so,
there are two different ways that we might execute a call: by stepping over it and
by stepping into it. Most IDE debuggers have these two possibilities, and it is
essential that you understand the difference.
Stepping over a call
We describe what it means to step over a call. Suppose we are executing this
call to procedure printSums :
PrintExample.printSums(20, 6);
We have assigned the arguments to the parameters, so that we have this situation:
Java console
b 20
c 6
We are ready to execute the statements in the method body. The first state-
ment is a function call printSum(b, c) . We execute it by stepping over the call.
To do this, we do what the specification of the procedure says to do: print the
larger of b and c . So, we place 26 in the Java console, yielding this state:
Java console
b 20
Thus, stepping over a call means simply to execute it as an indivisible
action, doing what the specification says to do.
Stepping into a call
Now, the second statement is to be executed: printSum(b, c * c); . We
execute this statement using the second method, stepping into the call . To do this,
we go through the detailed steps mentioned earlier: assign the arguments of the
call to the parameters of the method and then execute the method body. In this
case, the parameter names are b and c . To avoid mixing up the parameters b and
c for this new method call with those that already exist, we place them in boxes
as shown below. Each box has in its upper left a subbox that contains the name
of the method called.
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