Clock exercise in Java

I am a novice in this java and I just started classes, they have sent us this exercise:

Exercise 3

1. Design a called class Relojwith the integer attributes: hora(24 hours), minutoand segundo, and the following methods:

2. A constructor that initializes attributes to values ​​passed as parameters.

3. A method called Increment that increments the time by one second.

For example:

17:53:59will be17:54:00

17:59:59will be18:00:00

4.A method called Decrement that decreases the time by one second.

For example:

17:53:00will be17:52:59

17:00:00will be16:59:59

5.A method called Hora12that converts to Stringthe time by concatenating its attributes and returns the string in the 12-hour format ( hh:mm:ss AM/PM)

AM: (until 12 noon), PM (from 12 to 24 hours)

This is my code, Class Reloj:

public class Reloj {
    int modo,hora, minutos,segundos;

    int getmodo(){

    return modo;

    }


    public void setmodo(int modo){

    this.modo=modo;
    }

    int gethora(){

    return hora;

    }


    public void sethora(int hora){

    this.hora=hora;
    }

    public int getminutos(){

    return minutos;

    }


    public void setminutos(int minutos){

    this.minutos=minutos;
    }

    public  int getsegundos(){

    return segundos;

    }


   public  void setsegundos(int segundos){

    this.segundos=segundos;
    }

   public  Reloj(){
    modo=24; /*por defecto ponemos 24horas*/
    hora=0;
    minutos=0;
    segundos=0;


    }

    public Reloj( int h, int m, int s){
        this.modo=24;
        this.hora=h %24;
        this.minutos=m % 60;
        this.segundos=s % 60;

    }


   public void ponerEnHora(int md, int hh, int mm, int ss){
      modo=md;
      hora=hh % 24;
      minutos=mm % 60;
      segundos=ss % 60;
   }

   public void incrementar(){
    segundos++;
    if (segundos==60){
    segundos=0;
    minutos++;
    if(minutos==60){
    minutos=0;
    hora=(hora+1)%24;
    }

    }

    }

   public void decrementa(){
    segundos--;
    if(segundos<00){
        segundos=59;
        minutos--;
        if(minutos<00){
        minutos=59;
        hora=(hora-1) %24;

        }
    }
   }
   public String verHora(){

       String hms="Son las ";

       if (modo==12){//modo 12 horas    
           hms+=(hora>12)?hora-12:hora;
           hms+= ":"+minutos+":"+segundos;
           hms+=(hora>=12)?"pm":"am";

       }else{//modo 24h
       hms+=hora+":"+minutos+":"+segundos;
       }
   return (hms);
   }
}

Clock class MAIN:

public class Relojes {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        Reloj reloj1 = new Reloj();
        reloj1.ponerEnHora(24,17,10,10);
        System.out.println(reloj1.verHora());
        reloj1.incrementar();
        System.out.println(reloj1.verHora());
        reloj1.decrementa();
        System.out.println(reloj1.verHora());

    }

}

I don't get the hours in 12H mode, everything else works, but it doesn't work for me to print the 12h mode with AM or PM, let's see if you can give me a hand.