Classes and objects in Java - JavaTech: An Introduction to Scientific and Technical Computing with Java - page 75

applets via the applet tag parameters. An applet hypertext tag includes the param
sub-tag:
<applet...>
< param name =" string1 " value =" string2 ">
< /applet >
The name parameter provides an identifier for the string passed in the value
parameter to the applet program. For example, we could pass two numbers as
follows:
< applet code =" MyApplet " width =" 100 " height =" 50 ">
< param name =" fpNumber " value =" 12.45 ">
< param name =" intNumber " value =" 10 ">
< /applet >
To obtain the parameter values the Applet class provides this method:
String getParameter (String paramName);
The parameter returns as a string from this method so we need to convert it to a
numerical primitive type value. The wrapper classes provide tools for this in the
form of static methods. (Since they are static, they can be called without having an
instance of the wrapper class.) This is illustrated in the following example code:
public void init () {
string fpStr = getParameter ( " fpNumber " );
double fpNum = Double.parseDouble (fpStr);
String intStr = getParameter ( " intNumber " );
int intNum = Integer.parseInt (intStr);
....
Here the getParameter (String) method returns the string value for
the fpNumber parameter, and the static method Double.parseDouble
(String) from the Double wrapper class converts it to a double value.
Similarly, we get the integer parameter using the parseInt (String) static
method from the Integer class.
The parseInt() method has been available since Java 1.0, but
parseDouble() only appeared with Java 1.2. Previously, the valueOf()
method was used to return a Double value, which in turn could provide the
double primitive value using the doubleValue() method:
double fpNum = Double.valueOf(fpStr).doubleValue();