数组列表。 ArrayList为int和double

Question

I have the problem that I can't take a number from the arraylist and make it into a int or double which I have to do to cacluate the BMI using weight and height. Please have a look!
The assignment is to put in guests' weight, length, and name and sort the ones with a bad length to height ratio out. In the main I create an array with a couple of guests and when I run it says:

"Exception in thread "main" java.lang.NumberFormatException: For input string "name"

and

java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Integer.parseInt(Integer.java:492)
at java.lang.Integer.parseInt(Integer.java:527)
at Diet.putOnDiet(Diet.java:12)
at TestDiet.main(TestDiet.java:7)

The Diet class is as follows:

public class Diet{

    public static ArrayList<Guest> putOnDiet(ArrayList <Guest> list){
        ArrayList<Guest> namn = new ArrayList<Guest>();
        ArrayList<Guest> hej = new ArrayList<Guest>();
        for(int i = 0; i<=list.size()/3; i = i+3){

            int langd = Integer.parseInt(list.get(i+1).toString()); //I dont know how to make this work
            double vikt = Double.parseDouble(list.get(i).toString());
            String name = list.get(i+2).toString();

            if ((vikt) > 1.08*(0.9*(langd -100))){
                namn.add(new Guest(vikt, langd, name));
            }
        }

        return namn;
    }
}

And the Guest class:

public class Guest { 

   private double weight; private double length; private String name; 

   public Guest(double weight, double length, String name){ 
      this.name = name; this.weight = weight; this.length = length; // Maybe the problem is here. How do you modify the class to make it work?
   } 
   public String getName() {
      return name; 
   } 
   public double getWeight() 
   { 
      return weight; 
   } 
   public double getLength() { 
      return length; 
   } 
   public void setName(String name) { 
      this.name = name; 
   } 
   public void setWeight(double weight) { 
      this.weight = weight; 
   } 
   public void setLength(double length) 
   { this.length = length; 
   } 
   public boolean isSlim() { 
      if (weight >= 1.08 * 0.9 * (length - 100)) { 
         return false; 
      }
      else 
         return true; 
   }
   public String toString() { 
      return name + "\n" + weight + "\n" + length; 
   } 
}

Answer 1

Are you sure that the you are parsing an integer?

Well number parsing exception is thrown when it can't parse the number. When the string is not a number like "somthing#$%^&". So try replacing this line

int langd = Integer.parseInt(list.get(i+1).toString());

with this

try {
       int langd = Integer.parseInt(list.get(i+1).toString());
} catch (NumberFormatException e) {
       System.out.println(list.get(i+1).toString() +" : This is not a number");
       System.out.println(e.getMessage());
}

EDIT After reading WOUNDEDStevenJones answer I also think you should not be even using toString() or parsing methods. See WOUNDEDStevenJones answer for more details.

Answer 2

It looks like you'll want to change it to

for (int i=0; i<list.size(); i++) {
    double langd = list.get(i).getLength();
    double vikt = list.get(i).getWeight();
    String name = list.get(i).getName();
}

and kind of ignore your getString() method for this purpose

Note: I'm not sure what you're trying to do with your different indexes, but they'll probably all be .get(i)

Answer 3

The method list.get(i) will return an object of type Guest . Guest has methods, getWeight() and getLength() .

list.get(i).getWeight() 

This would actually give you a double value in return. And,

Integer.parseInt(list.get(i).getWeight().toString()) 

This should be able to parse.

Hope this helps.

_san