Java Reference
In-Depth Information
Passing Arguments to Methods
Javapassesargumentstomethodsviaastyleofargumentpassingcalled pass-by-value ,
which the following example demonstrates:
Employee emp = new Employee("John ");
int recommendedAnnualSalaryIncrease = 1000;
printReport(emp, recommendAnnualSalaryIncrease);
printReport(new Employee("Cuifen"), 1500);
Pass-by-valuepassesthevalueofavariable(thereferencevaluestoredin emp orthe
1000valuestoredin recommendedAnnualSalaryIncrease ,forexample)orthe
valueofsomeotherexpression(suchas new Employee("Cuifen") or 1500 )to
the method.
Becauseofpass-by-value,youcannotassignadifferent Employee object'sreferen-
ceto emp frominside printReport() viathe printReport() parameterforthis
argument. After all, you have only passed a copy of emp 's value to the method.
Many methods (and constructors) require you to pass a fixed number of arguments
when they are called. However, Java also can pass a variable number of argu-
ments—such methods/constructors are often referred to as varargs methods/construct-
ors .Todeclareamethod(orconstructor)thattakesavariablenumberofarguments,spe-
cify three consecutive periods after the type name of the method's/constructor's right-
mostparameter.Thefollowingexamplepresentsa sum() methodthatacceptsavari-
able number of arguments:
double sum(double... values)
int total = 0;
for (int i = 0; i < values.length; i++)
total += values[i];
return total;
sum() 's implementation totals the number of arguments passed to this method;
for example, sum(10.0, 20.0) or sum(30.0, 40.0, 50.0) . (Behind the
scenes, these arguments are stored in a one-dimensional array, as evidenced by val-
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