problems with for loop

Code :

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	case 3:
		System.out.println("Hundens namn: ");
	    String todelete=scan.nextLine();
 
         for (Dog h : dogs)
	    	if (h.getname().equals(todelete))
            {
                System.out.println(h);
	    		dogs.remove(h);
	    		System.out.println();
	    		System.out.println(h+ " Är borttagen ");
            }
	    break;

---

Exception in thread "main" java.util.ConcurrentModificationException
at java.util.AbstractList$Itr.checkForComodification( AbstractList.java:372)
at java.util.AbstractList$Itr.next(AbstractList.java: 343)
at Register.main(Register.java:68)

Thats the errormessage. The program runs fine except for when I want to delete an item it shows me the errormessage above. Whats wrong?

Did you read the API doc for the exception that is thrown?

Try using a normal for loop to iterate through the collection.

Norm what do you mean, using a normal for loop? I have tryed but I cant seem to make this one work. Is the last piece of my assignment...

Quote:

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normal for loop?

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Code :

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 for(int i=0; i < collection.size(); i++) {
             Type item = collection.get(i);
             ...
          }

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What happened when you use this type of loop?

I can't make it work @Norm =/

Make a small, simple program that compiles, executes and shows the problem.

Post the full text of the error messages you are getting.

Code :

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import java.util.ArrayList;
import java.util.Scanner;
import java.util.Iterator;
 
 
 
public class Register{
	public static void main(String []args){
 
		double tailLength;
 
		ArrayList<Dog> dogs = new ArrayList<Dog>();
 
		for(;;){
			System.out.println();
			System.out.println("Make a choice:");
			System.out.println("----------------------");
			System.out.println();
			System.out.println("1. Registrera new dog");
			System.out.println("2. List the dogs");
			System.out.println("3. Delete dog");
			System.out.println("4. Exit");
 
			Scanner keyboard= new Scanner(System.in);
 
			int choice = Integer.parseInt (keyboard.nextLine());
 
			switch (choice){
			case 1:
				System.out.println("Hundens namn: ");
				String name=keyboard.nextLine();
 
				System.out.println("Hundens vikt (kg): ");
				int weight=Integer.parseInt(keyboard.nextLine());
 
				System.out.println("Hundens Œlder: ");
				int age=Integer.parseInt(keyboard.nextLine());
 
				System.out.println("Ras: ");
				String race=keyboard.nextLine();
 
				tailLength=(double)age*weight/10;
				if ("Tax".equalsIgnoreCase(race))
					tailLength=3.7;
 
				Dog dogx = new Dog(name,weight,age,race,tailLength); 
				dogs.add(dogx);
				System.out.println(dogx);
 
				break;
 
			case 2:
 
				System.out.println("Ange svanslŠngd: ");
				int minimumTailLength=Integer.parseInt(keyboard.nextLine());
				for (int x=0; x<dogs.size(); x++){
					tailLength = dogs.get(x).getTailLength();		
 
					dogs.get(x);
					if (tailLength >= minimumTailLength)
						System.out.println(dogs.get(x));
				}
				break;
 
			case 3:
//See below!
 
 
				break;
 
			case 4: 
			{
				System.exit(0);
			}
 
			break;
 
			default:
			{
				System.out.println("Fel val, try igen. ");
			}
			break;
			}
		}
 
 
	}
}

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Code :

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public class Dog{
 
	//Instansvariabler
	private String name;
	private int weight;
	private int age;
	private String race;
	private double tailLength;
 
 
	public Dog (String name, int weight, int age, String race, double tailLength){
		//Variabler ges i konstruktorn
		this.name=name;
		this.weight=weight;
		this.age=age;
		this.race=race;
		this.tailLength=tailLength;
 
	}
 
	public double getTailLength(){ 
		return tailLength;
	}
 
	public String getName(){
		return name;
	}
 
	public String toString(){
		return ("Hunden "+name+" Šr en "+race+ " som vŠger: "+weight+ "Kg.\nDen Šr "+age+" "+"Œr gammal, "+"svanslŠngd: "+tailLength+" cm");
	}
 
}

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Code :

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                       case 3:
 
                                System.out.println("Hundens namn: ");
                            String toDelete=keyboard.nextLine();
 
                         for (Dog deletedog : dogs)
                                if (deletedog.getname().equals(toDelete))
                            {
                                        dogs.remove(deletedog);
                                        System.out.println();
                                        System.out.println(deletedog.getname() + " är borttagen");
                            }
                                        break;

---

So thats the code entire program. 2 classes when pressing 3 you should be able to delete a dog from the register.
when deleting I get this error message

Errormessage:
Exception in thread "main" java.util.ConcurrentModificationException
at java.util.AbstractList$Itr.checkForComodification( AbstractList.java:372)
at java.util.AbstractList$Itr.next(AbstractList.java: 343)
at Register.main(Register.java:71)

Code :

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for (Dog deletedog : dogs)

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You are still using this syntax for the for loop. You need to use the syntax I suggested in post#4.


The code you posted does NOT compile, execute and show the problem.