Java - ArrayList in object

Question

I'm getting the following error:

cannot find symbol
 for(Component c : first.caseComponents){
 ^
 symbol: variable caseComponents
 location: variable first of type Component

Here is my code:

import java.util.List;
import java.util.ArrayList;
import java.util.Iterator;
import java.lang.Iterable;
import java.util.LinkedList;
import java.util.Queue;
public class Composite extends Component implements Iterable<Component>{
 private List<Component> caseComponents = new ArrayList<Component>();
 public Composite(String nameIn, int weightIn) {
 super(nameIn, weightIn);
 }
 @Override
 public Iterator<Component> iterator(){
 return new CompIterator();
 }
 private class CompIterator implements Iterator{
 int index = 0;
 @Override
 public boolean hasNext(){
 if(index<caseComponents.size()){
 return true;
 }
 return false;
 }
 @Override
 public Object next() {
 if(this.hasNext()){
 return caseComponents.get(index++);
 }
 return null;
 }
 }
 public String breadthFirst() {
 Queue<Component> q = new LinkedList<Component>();
 StringBuilder stringRep = new StringBuilder();
 q.add(this);
 while(q.element()!=null){
 Component first = q.remove();
 System.out.println(first.name);
 if (first instanceof Composite){
 Composite comp = (Composite)first;
 for(Component c : comp.caseComponents){
 q.add(c);
 }
 }
 }
 }
}

And also the Component.java file:

public abstract class Component {
 protected String name;
 protected int weight;
 public Component(String nameIn, int weightIn){
 this.name=nameIn;
 this.weight=weightIn;
 }
 public abstract int getWeight(); //abstract method.
 public abstract String toString();
}

It seems that my type casting does not work and the object comp is still seen as an instance of Component instead of Composite, which has a variable caseComponents. How can I fix this?

• Nathan Tuggy: Your error message does not match the posted code, which has no for(Component c : first.caseComponents){ line.
• Thilo: @NathanTuggy: It was there. Now edited to a fixed version. Not sure what the question is about now....

Answer 1

You need to make the loop actually use the typecast:

if (first instanceof Composite){
 Composite comp = (Composite)first;
 // use "comp" here: 
 for(Component c : comp.caseComponents){
 q.add(c);
 }
}

In your code, comp was never actually used anywhere.

• mkobit: @Shhua if this is the correct answer, please mark it as such.