Error: Could not find or load main class <<< Why do I get this error?

Question

I can't seem to get this code to work correctly. This is the error I keep getting:

Error: Could not find or load main class.

What causes this?

Payroll3.java

// A program to calculate and print the department, name, and pay of an employee.
import java.util.Scanner; //program uses the Scanner class
import java.io.*;

class main
{
public class Payroll3

{
// main method begins execution of Java program.
    public void main(String args[])
          {
   // create Scanner to obtain input from the command window
   Scanner input = new Scanner (System.in);

   double number1; // first number to multiply
   double number2; // second number to multiply
   double product; // product of number1 and number2


while(true){   // infinite loop


   System.out.print("Enter Department name: "); //prompt
   String name = input.nextLine(); // read name from user

    if(name.equals("stop"))  // exit the loop
        break;


   System.out.print("Enter number of employees: "); // prompt
   number1 = input.nextDouble(); // read first number from user
   input.nextLine();
      while( number1 <= -1){
         System.out.print("Enter positive number of employees:"); // prompt
         number1 = input.nextDouble(); // read first number from user
         input.nextLine();
      } /* while statement with the condition that negative numbers are entered
         user is prompted to enter a positive number */

   System.out.print("Enter average salary: "); // prompt
   number2 = input.nextDouble(); // read second number from user
   input.nextLine();
      while( number2 <= -1){
       System.out.print("Enter positive number for average salary:"); // prompt
        number2 = input.nextDouble(); // read first number from user
        input.nextLine();                    
 } /* while statement with the condition that negative numbers are entered
         user is prompted to enter a positive number */

   // make department object
        Department dept = new Department(name,number1,number2);

   product = number1 * number2; // multiply numbers

   System.out.println("Department name:" + name); // display Department name
   System.out.printf("Payroll is: $%.2f\n", product); // display product

   } // end while method

} // end method main

}/* end class Payroll3 */
}

//  Stores data about an department
class Department {

//fields
String name;
double number1;
double number2;

// constructor
public Department(String name, double number1, double number2) {
    this.name = name;
    this.number1 = number1;
    this.number2 = number2;
}

// returns the pay:
public double getPay() {
    return number1*number2;
}

// getters and setters

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public double getnumber1() {
    return number1;
}

public void setNumber1(double number1) {
    this.number1 = number1;
}

public double getNumber2() {
    return number2;
}

public void setNumber2(double number2) {
    this.number2 = number2;
}


}

Answer 1

Class must be public and main must be static

public static void main(String argv[])

And you can't have nested main class. At least it's probably not what you expect. Why don't you start with simple tutorial and expand it with your code?

Answer 2

while Running the program just type java program_name but NOT java program_name.java