Arraylist only with approved students

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Arraylist only with approved students

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#1 by (1 votes)

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Good I have an exercise carried out where I introduce a series of data of students and I keep them in an arraylist. What I want is to save in another arraylist only the students whose average grade is greater than or equal to 5 but I do not know how to start

Here the code:

 public class Principal 
 {

    public static void main(String[] args)
    {
        System.out.println("EJERCICIO ARRAYLIST EN JAVA\n");

        Scanner tecla = new Scanner (System.in);
        ArrayList <Alumnos> ArrayListAlumnos = new ArrayList();
        Alumnos objAlumnos = new Alumnos();
        Fecha objFecha = new Fecha();


        //Introducimos datos
        for(int i=0;i<2;i++)
        {
            objAlumnos = new Alumnos();
            objFecha = new Fecha();
            int notas[] = new int [3];

            System.out.print("\nNumero de expediente del "+(i+1)+" alumno: ");
            objAlumnos.setNumeroExpediente(tecla.nextInt());
            tecla.nextLine();//Limpiar buffer
            System.out.print("Dni: ");
            objAlumnos.setDni(tecla.nextLine());
            System.out.print("Nombre y apellidos: ");
            objAlumnos.setNombre(tecla.nextLine());
            System.out.println("Introduca fecha de nacimiento");
            do{             
                System.out.print("Dia(1-31): ");
                objFecha.setDia(tecla.nextInt());                               
                System.out.print("Mes(1-12): ");
                objFecha.setMes(tecla.nextInt());
                System.out.print("Año(1980-1999): ");
                objFecha.setAnio(tecla.nextInt());
                if(objFecha.fechaCorrecta()==false)
                {
                    System.out.println("\nFecha de nacimento incorrecta, introduzca de nuevo");
                }
            }while(objFecha.fechaCorrecta()==false);            
            tecla.nextLine();//Limpiar buffer
            System.out.print("Curso: ");
            objAlumnos.setCurso(tecla.nextLine());
            System.out.println("\nIntroduzca notas correspondientes(1-10)");            
            for(int j=0;j<3;j++)
            {               
                int nota;
                do{
                    System.out.print("Nota "+(j+1)+" : ");
                    nota=tecla.nextInt();   
                    if(nota<1 || nota>10)
                    {
                        System.out.println("\nLa notas deben ir del 1 al 10, introduzca de nuevo");
                    }
                }while(nota<1 || nota>10);

                notas[j]=nota;
            }   

            System.out.println("La media de las notas es: " + calcularMedia(notas));
            objAlumnos.setNotas(notas);     
            objAlumnos.setFecha_nacimiento(objFecha);
            ArrayListAlumnos.add(objAlumnos);
         }

        //Visualizamos
        System.out.println("\n\nDATOS INTRODUCIDOS\n");
        for(int i=0;i<ArrayListAlumnos.size();i++)
        {
            objAlumnos = ArrayListAlumnos.get(i);
            System.out.println(ArrayListAlumnos.get(i));
        }
    }

    public static double calcularMedia(int[] notas)
    {
        double resultado = 0;

        for(int nota: notas)
        {
            resultado+=nota;
        }
        return resultado/notas.length;      
    }   
}

Another possibility, that does not require modifying your code, only an addition, is that when you have saved all the students, you go through the arrayList and store in another that you only believe those that meet your criteria, this can be done for example by creating A new method that receives an ArrayList as an argument, and runs through it to do what you require with the student objects inside.

Greetings.

java poo arraylist

asked by Mario Guiber 27.08.2017 в 10:54

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1 answer

How to increase 30 days to a date by saving data in a table? [duplicate] Can not resolve symbol 'R'

score 1 · Accepted Answer

You are creating a ArrayList called "ArrayListAlumnos", where you save all the students:

ArrayList <Alumnos> ArrayListAlumnos = new ArrayList();

You just have to create another one for those approved:

ArrayList <Alumnos> ArrayListAlumnosAprob = new ArrayList();

In the data entry loop, at the end you are saving the object student with his data in "ArrayListAlumnos":

ArrayListAlumnos.add( objAlumnos );

You have to do the same with the approved ones, in the new ArrayList , but within a conditional:

if ( nota >= 5 ) {

    ArrayListAlumnosAprob.add( objAlumnos );    
}

and as a note, you are stating it in a loop, you declare it outside and before, so that it is visible when using it in the conditional:

System.out.println("\nIntroduzca notas correspondientes(1-10)"); 
int nota = 0; //Nueva declaración y le asigno un valor para evitar problemas
for(int j=0;j<3;j++)
{               
    //int nota; //antigua declaración (visibilidad solo en el bloque)
    do{
        System.out.print("Nota "+(j+1)+" : ");
        nota=tecla.nextInt();   
        if(nota<1 || nota>10)
        {
            System.out.println("\nLa notas deben ir del 1 al 10, introduzca de nuevo");
        }
    }while(nota<1 || nota>10);

    notas[j]=nota;
}