Thread: HashSet cannot be cast to java.util.ArrayList

public class Employee{
 
    private int id;
    private String name;
    private String address;
    private double salary;
//setter & getter
}

public class test{
 
		ArrayList check= coll (); 
		CheckCollection(check);
 
public static ArrayList coll (){
 
		ArrayList list = new ArrayList();
		Set set = new HashSet();
 
Employee ts1 = new Employee (10, "Jad", "L.A", 200.0);
        Employee ts2 = new Employee (11, "Amal", "Berlin", 600.0);
        Employee ts3 = new Employee (12, "Jasmin", "London", 250.0);
        Employee ts4 = new Employee (10, "sam", "Paris", 200.0);
        Employee ts5 = new Employee (14, "Adam", "NY", 210.0);
 
set.add(ts1);
set.add(ts2);
set.add(ts3);
set.add(ts4);
set.add(ts5);
 
//now convet the Set to List
list.add(set);
 
return list;
}
 
public static void CheckCollection(ArrayList data) {
ArrayList xxx= null;
for (int i = 0; i < data.size(); i++) {
 
	       	    xxx = (ArrayList)data.get(i);
}
}

any way when i run it i get error:

HTML Code:

java.lang.ClassCastException: java.util.HashSet cannot be cast to java.util.ArrayList

so why i thought i could convert the Set totally to List Type !!

Are you asking us why you thought what you thought? We can't answer that.

If you're also wondering how to convert a HashSet to an ArrayList, here's an example of how to do that:

// found here:
// http://www.xyzws.com/javafaq/how-to-convert-a-hashset-to-an-arraylist/180
 
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
 
public class TestClass {
 
  public static void main(String[] args) {
 
    Set<String> hashset = new HashSet<String>();
    hashset.add("A");
    hashset.add("B");
    hashset.add("C");
    List<String> list = new ArrayList<String>(hashset);
    System.out.println(list.toString());
 
  }
}

ok the same what i did, i also make the same

ArrayList list = new ArrayList(set);

but still get the error

If you want help with updated code, please post it. We can't accurately imagine what you've done.

ArrayList list = new ArrayList(set);

but still get the error[/QUOTE]
No, that change is not equivalent to what I posted. This is:

public class TestClass
{
    // modified to simply make the point, not provide the same function
    public static void coll()
    {
        Set<Employee> set = new HashSet<Employee>();
 
        Employee ts1 = new Employee (10, "Jad", "L.A", 200.0);
        Employee ts2 = new Employee (11, "Amal", "Berlin", 600.0);
        Employee ts3 = new Employee (12, "Jasmin", "London", 250.0);
        Employee ts4 = new Employee (10, "sam", "Paris", 200.0);
        Employee ts5 = new Employee (14, "Adam", "NY", 210.0);
 
        set.add(ts1);
        set.add(ts2);
        set.add(ts3);
        set.add(ts4);
        set.add(ts5);
 
        //now convet the Set to List and print the results
        ArrayList<Employee> list = new ArrayList<Employee>(set);
        System.out.println( list.toString() );
 
        // this is your old line, commented out
//        list.add(set);
 
    } // end method coll()
 
    public static void main( String[] args )
    {
        coll();
    }
}