如何打印阵列列表，以及如何向阵列列表添加错误检查？

Question

I have been trying to solve this problem for ages and with no luck I didn't progress. Could someone please help me out. I have created an arrayList, made an getter class, have made a method. I can add stuff to the array list as well but when I print the arrayList out it prints out some random text.

below is the arrayList I created.

public static ArrayList<getArrayList> arrayList = new ArrayList<getArrayList>();

here is my method;

private static void addToArrayList(String a, double no1, int no2, int no3) {

        try {
            arrayList.add(new getArrayList(a, no1, no2, no3));
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

here is my getter class

public class getArrayList {
    private String name;
    private double seconds;
    private int speed1;
    private int speed2;


    public String getName() {
        return name;
    }



    public double getSeconds() {
        return seconds;
    }



    public int getSpeed1() {
        return speed1;
    }



    public int getSpeed2() {
        return Speed2;
    }



    public StoreCommands(String storeName, double storeSeconds, int storeSpeed1, int storeSpeed2) throws Exception{
        name =  storeName;
        seconds = storeSeconds;
        speed1 = storeSpeed1;
        speed2 = storeSpeed2;

        }

    }

to add stuff on this list I use the method I created

addToArrayList(String a, double no1, int no2, int no3) filled in with my values

and to receive stuff from the arraylist I use this

  for(getArrayList s : arrayList) {
System.out.println(arrayList + "\n")
        ;

and it prints out if i use System.out.println(arrayList), depending on how much I add to the arraylist.

[StoreCommands@49a21b63]

Besides that could someone tell me how I can set a size of the arrayList so if anything more that is being added it won't add and give an error. Also I need to perform certain error checks once the items are in the arrayList *1st If the an item is added to the list and the user tries to add the same one again straight after I want to display an error.. (the user can add the same stuff but not directly after the one they just added, they will need to add something else first) *2nd if say user wants to add apples to the list, I want to limit that to only 2 time in the whole list, more than that will not be added and will display and error.

Could someone help me out please, I will really appreciate it.

Thanks.

Answer 1

Try this -

for(getArrayList s : arrayList)
     System.out.println(s + "\n");//This print the tostring of getArrayList class

Again override the toString method of getArrayList class, to print actual field value of the object. Example -

public class getArrayList {
     public String toString(){
          return name +"||" +seconds+"||"+ speed1+"||"+speed2;
     }
}

Note : Follow java nomenclature standard, first later of you class name would be capital And also give a relevent name to the Class.

Answer 2

You don't have to loop in order to print an array, just do:

System.out.println(Arrays.toString(arrayList.toArray()));

ArrayList doesn't have a mechanism to limit the size, if you want to do it - you'll have to implement it.

Example:

import java.util.ArrayList;    
/**
 * User: alfasin
 * Date: 2/5/14
 */
public class RestrictedSizeArrayList<E> extends ArrayList<E> {

    private static final int limit = 6;//example

    @Override
    public boolean add(E e){
        if(this.size() > 5){
            throw new IndexOutOfBoundsException("Can't add more than 5 elements to the ArrayList");
        }
        boolean result = super.add(e);
        return result;
    }
}

Answer 3

Overriding toString method will help you to print actual data. Override it in your class getArrayList . One more thing is class name should start with capital letter.

public String toString()
{
    return "Name  :  "+name+"  Seconds  : "+seconds+"  Speed1  :  "+speed1+"  Speed2  :  "+speed2;
}

and use it like

for(getArrayList s : arrayList)
   System.out.println(s.toString);

You can limit the size by adding check to

private static void addToArrayList(String a, double no1, int no2, int no3) {

        try 
        {
           if(arrayList.size < 10) //any size you want
             arrayList.add(new getArrayList(a, no1, no2, no3));
           else
             System.out.println("ArrayList is full");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }