Java项目中每一个类都可以有一个main方法

Java项目中每一个类都可以有一个main方法，但只有一个main方法会被执行，其他main方法可以对类进行单元测试。

public class StaticTest {
    public static void main(String[] args)
    {
        Employee[] staff=new Employee[3];
        staff[0]=new Employee("Tom",40000);
        staff[1]=new Employee("Dick",60000);
        staff[2]=new Employee("Harry",65000);
        for(Employee e:staff)
        {
            e.setId();
            System.out.println("name="+e.getName()+",id="+e.getId()+",salary="+e.getSalary());
        }
        int n=Employee.getNextId();
        System.out.println("Next available id="+n);
    }
}

class Employee
{
    public Employee(String n,double s)
    {
        name=n;
        salary=s;
        id=0;
    }
    public String getName()
    {
        return name;
    }
    public double getSalary()
    {
        return salary;        
    }
    public int getId()
    {
        return id;
    }
    public void setId()
    {
        id=nextId;
        nextId++;
    }
    public static int getNextId()
    {
        return nextId;
    }
    public static void main(String[] args)
    {
        Employee e=new Employee("Harry",50000);
        System.out.println(e.getName()+" "+e.getSalary());
    }
    private String name;
    private double salary;
    private int id;
    private static int nextId=1;
}

java Employee可以得到

Harry 50000.0

java StaticTest可以得到

name=Tom,id=1,salary=40000.0

name=Dick,id=2,salary=60000.0

name=Harry,id=3,salary=65000.0

Next available id=4