Java Reference
In-Depth Information
In Java, the concept of a method, whether predefined or user-defined, is similar to that of
a function in algebra. For example, every method has a name and, depending on the
values specified by the user, it does some computation. This section discusses various
predefined methods.
Some of the predefined mathematical methods are pow(x, y) and sqrt(x) .
The power method, pow(x, y) , calculates x y ; that is, the value of pow(x, y) is x y .
For example, pow(2, 3) is 8.0 and pow(2.5, 3) is 15.625 . Because the value of
pow(x, y) is of type double , we say that the method pow is of type double or that the
method pow returns a value of type double . Also, x and y are called the parameters
(or arguments) of the method pow . The method pow has two parameters.
The square root method, sqrt(x) , calculates the nonnegative square root of x for
x >= 0.0 . For example, sqrt(2.25) is 1.5 . The method sqrt is of type double and
has only one parameter.
In Java, predefined methods are organized as a collection of classes, called class libraries.
For example, the class Math contains mathematical methods. Table 7-1 lists some of
Java's predefined mathematical methods. The table gives the name of the method (in bold
type), number of parameters, the data type of the parameters, and the method type. The
method type is the data type of the value returned by the method. The table also shows
how a method works. The class Math is contained in the package java.lang .
7
TABLE 7-1 Some Predefined Mathematical Methods and Named Constants
class Math (Package: java.lang )
Named Constants
double E ;
E = 2.7182818284590455
double PI ;
PI = 3.141592653589793
Methods
Expression
Description
Returns the absolute value of x .If x is of type int , it returns a value of
type int ;if x is of type long , it returns a value of type long ;if x is of
type float , it returns a value of type float ;if x is of type double ,it
returns a value of type double .
Example: abs(-67) returns the value 67
abs(35) returns the value 35
abs(-75.38) returns the value 75.38
abs(x)
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