no se puede convertir a java.lang.Comparable

Question

import java.util.HashMap; 
import java.io.*; 
import java.util.*; 
public class Fegan implements Comparable{ 
HashMap<String, Integer> cart = new HashMap<String, Integer>(); 
List list = new ArrayList<FoodItems>(); 
int x =0; 
public void addToCart(FoodItems f) 
{ 
    cart.put(f.name, f.valueOfFood); 
} 
public String display(FoodItems f) 
{ 
    return(f.name + " costs " + f.valueOfFood); 
} 
public void addToList(FoodItems f) 
{ 
    //FoodItems temp = (FoodItems) f; 
    list.add(f); 
} 
public int compareTo(Object o) 
{ 
    //FoodItems temp = (FoodItems) o; 
    if(this.x == ((FoodItems)o).valueOfFood) 
     return 0; 
    else if (this.x <((FoodItems)o).valueOfFood) 
     return 1; 
    else 
     return -1; 
} 
public void sortMap(List list) 
{ 
    for(int i =0; i< list.size(); i++) 
    { 
     FoodItems temp = (FoodItems) list.get(i); 
     cart.put(temp.name, temp.valueOfItem); 

    } 
} 
} 

---

import java.util.Collections; 
import java.util.HashMap; 
import java.util.Iterator; 
import java.io.*; 
import java.util.*; 
public class Test { 
public static void main(String [] args) 
{ 
    HashMap<String, Integer> cart = new HashMap<String, Integer>(); 
    FoodItems firts = new FoodItems("Chocolate" , 50); 
    FoodItems second = new FoodItems("Juice", 79); 
    FoodItems third = new FoodItems("Apple", 200); 
    FoodItems forth = new FoodItems("Orange", 300); 
    FoodItems fifth = new FoodItems("Milk" , 400); 
    ArrayList items = new ArrayList(); 
    items.add(firts); 
    items.add(second); 
    items.add(third); 
    items.add(forth); 
    items.add(fifth); 
    Collections.sort(items); 
    Iterator itr = items.iterator(); 
    Fegan myFegan = new Fegan(); 
    myFegan.sortMap(items); 

    while(itr.hasNext()){ 
     Object element = itr.next(); 
     System.out.println(element + "\n"); 
    } 
} 
} 

¿Por qué es escribir

Exception in thread "main" java.lang.ClassCastException: FoodItems cannot be cast to java.lang.Comparable 
at java.util.ComparableTimSort.countRunAndMakeAscending(Unknown Source) 
at java.util.ComparableTimSort.sort(Unknown Source) 
at java.util.ComparableTimSort.sort(Unknown Source) 
at java.util.Arrays.sort(Unknown Source) 
at java.util.Collections.sort(Unknown Source) 
at Test.main(Test.java:21) 

Gracias de antemano!

Answer 1

• el objeto que implementa Comparable es Fegan.

El método compareTo está overidding en ella debe tener un objeto Fegan como un parámetro mientras que usted está lanzando a un FoodItems. Su implementación compareTo debe describir cómo se compara un Fegan con otro Fegan.

• para hacer realidad su clasificación, es posible que desee hacer su FoodItems aplicar Comparable aswell y copiar pegar su compareTo lógica real en ella.