Java - Ayuda como hacer un vector de objetos

--------------------Configuration: <Default>--------------------

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1

	at Lista.Agregar(Lista.java:19)

	at escuelita.main(escuelita.java:8)

Process completed.

import java.io.*;

class Alu

{

	private int mat,cfin,a,b;

	private String nom;

	private int faltas[]=new int[3];

	private int cal[]=new int[2];

	public Alu(int x)

	{

		mat=x;

		nom="sin nombre";

	}

	public Alu(int x, String y)

	{

		mat=x;

		nom=y;

	}

	public void setNom(String n){  nom=n;	}

	public String getNom()	{	return nom;	}

	public void setMat(int n){mat=n;	}

	public int getMat(){return mat;	}

	public void setCal(int x, int y){int a=x;int b=y;}

	public int getCal()	{	return cal[a]=b;}

	public void cFin(int x)	{	cfin=x;}

	public void setcFin(int x)	{	cfin=x;	}

	public int getcFin(){	return cfin;	}

	public float Promedio()

	{int prom=0;

		 prom=(cal[0]+cal[1])/2;

	System.out.println("Promedio: "+prom);

	return prom;

	}

	public int tFal()

	{int t;

		t=(faltas[0]+faltas[1]+faltas[2]);

		System.out.println("Faltas: "+t);

		return t;

	}

	public void imprimir()

	{

		System.out.println(nom+"	"+mat+" Final: "+cfin);

		tFal();

		Promedio();

	}

}

import java.io.*;

class Lista

{

	private String claveMat,nombre,prof;

	private Alu alumnos[];

	public Lista(String clave)

	{

		claveMat=clave;

		alumnos=new Alu[0];

	}

	public void Agregar(int x, String y)

	{   int n;

		Alu nuevo=new Alu(x,y);

		n=alumnos.length;

		Alu v[]=new Alu[n+1];

		nuevo.setMat(x);

		nuevo.setNom(y);

		v[n+1]=nuevo;

		alumnos=v;

	}

	public void imprimir()

	{

		int i;

		for(i=0;i<alumnos.length;i++)

			System.out.println(alumnos[i].getNom()+" "+alumnos[i].getMat() );

	}

}

import java.io.*;

public class escuelita

{

	public static void main(String mk[])

	{

		Lista gru=new Lista("10");

		gru.Agregar(11111,"JOSE");

		gru.imprimir();

	}

}