<%!
int number=0;
File file=new File("count.txt") ;
synchronized void countPeople()//计算访问次数的同步方法
{
if(!file.exists())
{
number++;
try {
file.createNewFile();
FileOutputStream out=new FileOutputStream("count.txt");
DataOutputStream dataOut=new DataOutputStream(out);
dataOut.writeInt(number);
out.close();
dataOut.close();
}
catch(IOException ee){}
}
else
{
try{
FileInputStream in=new FileInputStream("count.txt");
DataInputStream dataIn=new DataInputStream(in);
number=dataIn.readInt();
number++;
in.close();
dataIn.close();
FileOutputStream out=new FileOutputStream("count.txt");
DataOutputStream dataOut=new DataOutputStream(out);
dataOut.writeInt(number);
out.close();
dataOut.close();
}
catch(IOException ee){}
}
}
<%
countPeople();
%>
您是第
<%=number%>
个访问本站的客户。
例子4
Example2_4.jsp
<%@ page contentType="text/html;charset=GB2312" %>
请输入圆的半径：
<%!
public class Circle
{
double r;
Circle(double r)
{
this.r=r;
}
double 求面积()
{
return Math.PI*r*r;
}
double 求周长()
{
return Math.PI*2*r;
}
}
%>
<%
String str=request.getParameter("cat");
double r;
if(str!=null)
{
r=Double.parseDouble(str);
}
else
{
r=1;
}
Circle circle=new Circle(r); //创建对象。
%>
圆的面积是：
<%=circle.求面积()%>
圆的周长是：
<%=circle.求周长()%>
例子5
Example2_5.jsp
<%@ page contentType="text/html;charset=GB2312" %>
<%!
long continueSum(int n)
{
int sum=0;
for(int i=1;i<=n;i++)
{
sum=sum+i;
}
return sum;
}
%>
1到100的连续和:
<%
long sum;
sum=continueSum(100);
out.print(""+sum);
%>
