静的メソッドと静的フィールド

package test;

public class StaticTest {

	public static void main(String[] args) {
		// fill the staff array with three Employee objects
		Employee[] staff = new Employee[3];
		
		staff[0] = new Employee("Tom",40000);
		staff[1] = new Employee("Dick",50000);
		staff[2] = new Employee("Harry",60000);
		
		// print out information about all employee objects
		for (int  i = 0; i < staff.length; i++)
		{
			Employee e = staff[i];
			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
{
	private String name;
	private double salary;
	private int id;
      // ， 。 。
	private static int nextId = 1;
	
	public Employee(String n,double s){
		name = n;
		salary =s;
		id = 0;	
	}
	public String getName()
	{
		return name;
	}
	public void setName(String name){
		this.name = name;
	}
	public double getSalary(){
		return salary;
	}
	public void setSalary(double salary){
		this.salary = salary;
	}
	public int getId(){
		return id;
	}
	public void setId()
	{
		// set id to next avilable id
		id = nextId;
		nextId++;
	}
      // ， ， 。
	public static int getNextId()
	{
		return nextId; //return static field
	}
	
	public static void main(String[] args){
		Employee e = new Employee("Harry",50000);
		System.out.println(e.getName() + "\t" + e.getSalary());
	}
}

name=Tom, id=1, salary=40000.0
name=Dick, id=2, salary=50000.0
name=Harry, id=3, salary=60000.0
Next available id=4