Exception in thread "main" java.lang.NoSuchMethodError: main?

[Sakharam01]

Hello Friends,

I am beginner of java.
here i am facing run time exception for code
snippet which i am pasting here,please help me on this issue.

 
class Operation
{
int square(int n)
{
return n*n;
}
}
 
 
class Circle
{
Operation op;
double pi=3.14;
 
double area(int radius)
{
op=new Operation();
int rsquare=op.square(radius);
return pi*rsquare;
}
 
public static void main(String args[])
{
Circle c = new Circle();
double result = c.area(5);
 
System.out.println(result);
}
}

Regards
Sk.

[KevinWorkman]

Please post the full text of the error message, and show us exactly which line is throwing the Exception (since line numbers on the forum might not be the line numbers on your machine).

[Sakharam01]

Hello,

The problem has sorted out by my own,
thanks for reply.
i am facing problem in another source code here as

class Simple2
{
public static void main(String args[])
{
String s ="Altaf";
s.concat(" Shikalgar");
System.out.println(s);
}
}

it gives error as
[Simple2.java:3: cannot access String
bad class file : .\String.java
file does not contain class String
Please remove or make sure it appears in the correct sub directory of class path. ]

[KevinWorkman]

Did you create a new class named String? If so, rename it.

What version of Java are you running? How are you compiling this?