Classe Data e Classe DataTest

// Classe Data

public class Data {
    int dia;
    int mes;
    int ano;

    public Data(int novoDia, int novoMes, int novoAno){
        if(novoDia > 31 || novoDia < 1){
            this.dia = 1;
        }else{
            this.dia = novoDia;
        }

        if(novoMes > 12 || novoMes < 1){
            this.mes = 1;
        }else{
            this.mes = novoMes;
        }

        if(novoAno < 0){
            this.ano = 2001;
        }else{
            this.ano = novoAno;
        }
    }

    public Data(){
        this.dia = 1;
        this.mes = 1;
        this.ano = 2001;
    }

    public void setDia(int novoDia){
        if(novoDia > 31 || novoDia < 1){
            this.dia = 1;
        }else{
            this.dia = novoDia;
        }
    }
    public int getDia(){
        return this.dia;
    }

    public void setMes(int novoMes){
        if(novoMes > 12 || novoMes < 1){
            this.mes = 1;
        }else{
            this.mes = novoMes;
        }
    }
    public int getMes(){
        return this.mes;
    }

    public void setAno(int novoAno){
        if(novoAno < 0){
            this.ano = 2001;
        }else{
            this.ano = novoAno;
        }
    }
    public int getAno(){
        return this.ano;
    }

    @Override
    public String toString(){
        String data = "Data : "+ this.dia + " / "+ this.mes+" / "+this.ano;

        return data;
    }

    public void avancarDia(){
        if(this.dia == 31){
            this.dia = 1;
            if(this.mes == 12){
                this.mes = 1;
                this.ano = this.ano + 1;
            }
        }else{
            this.dia = this.dia + 1;
        }
    }
}

//Classe DataTest

public class DataTest {
    public static void main(String[] args){
        Data aniversario = new Data();
        Data prova = new Data(8,7,2014);

        aniversario.setDia(1454);
        aniversario.setMes(10);
        aniversario.setAno(1995);

        System.out.println("Dia :"+aniversario.getDia());
        System.out.println("Mes :"+aniversario.getMes());
        System.out.println("Ano :"+aniversario.getAno());

        System.out.println("Data do aniversario: "+aniversario.toString());

        prova.avancarDia();

        System.out.println("Data da prova: "+prova.toString());
    }
}