Here is the source code. I have marked as comments where the errors
are:
package Timeandahalf;

import javax.swing.JOptionPane;
import java.lang.String;

public class Timeandahalf {
public static void main( String args[] ) {

double total_wage;
int employee, hours, hourly;
String employee_number, hours_worked, hourly_rate;

for (int i=0; i<7; i++) {
employee_number = JOptionPane.showInputDialog(null,
"Enter employee number: ");
employee = Integer.parseInt( employee_number );

hours_worked = JOptionPane.showInputDialog(null,
"Enter hours worked for the week: ");
hours = Integer.parseInt( hours_worked );

hourly_rate = JOptionPane.showInputDialog(null,
"Enter hourly rate: ");
hourly = Integer.parseInt( hourly_rate );

total_wage = hours * hourly;
} // end of for (int i=0; i<7; i++)

if (hours > 40) { // variable hours might not have been initialized
total_wage = (hours * hourly) * 1.5; // variable hourly_rate
might not have been initialized
} // end of if hours_worked < 40

System.out.print("Employee number: ");
System.out.print(employee_number); // variable employee_number might
not have been initialized
System.out.print("Gross pay: ");
System.out.print(total_wage); // variable total_wage might not have
been initialized
System.exit( 0 );
}
}