java单利模式

package frank;
public class App
{
	public static void main(String[] args)
	{
		Person p1 = Person.getInstance();
		p1.setAge(10);
		Person p2 = Person.getInstance();
		System.out.println(p2.getAge());
	}
}
class Person
{
	private int age;
	private Person()
	{}
	private static Person instances;
	public static Person getInstance()
	{
		if(instances == null)
		{
			instances = new Person();
		}
		return instances;
	}
	public void setAge(int age)
	{
		this.age = age;
	}
	public int getAge()
	{
		return this.age; 
	}
}