乐友母婴怎么样:Java问题

我按照书上写的程序：

class Program3_4
{
interface java_emp
{
String office=new String("Java");
void status();
}

class abs_emp
{
int age,salary=0;
String name;
abs_emp(String a,int b,int c)
{
name=new String(a);
age=b;
salary=c;
}
public void status()
{
System.out.println("My name is"+name+".");
System.out.println("I am "+age+"old.");
System.out.println("I can earn $"+salary+" in one month.");
}
}

class employee extends abs_emp implements java_emp
{
employee(String a,int b,int c)
{
super(a,b,c);
}
public void status()
{
System.out.println("I am an employee of"+office);
System.out.println("My name is"+name+".");
System.out.println("I am "+age+"old.");
System.out.println("I can earn $"+salary+" in one month.");
}
}

class manager extends abs_emp implements java_emp
{
int manage_add;
private int total_salary;

manager(String a,int b,int c,int d)
{
super(a,b,c);
manage_add=d;
}
public void status()
{
total_salary=salary+manage_add;
System.out.println("I am manager of "+office);
System.out.println("My name is "+name+".");
System.out.println("I am "+age+"old.");
System.out.println("I can earn $"+total_salary+" in one month.");
}
}

public static void main(String arg[])
{
manager William=new manager("William",21,2000,500);
employee Joy=new employee("Joy",21,2000);
William.status();
Joy.status();
}
}

编译时提示说：non-static variable this cannot be referenced from a static context

我把main前的static去掉可以编译成功，但是有异常：NoSuchMethodError:main