如何从具有数组列表的类中调用方法到另一个类？

Question

I'm in my first semester of Java and I need help in calling methods from the VotingMachine class below to the Candidate Class. The Voting Machine class is compiling properly. Thank you all for any help you can provide.... Mercedes

import java.util.ArrayList;

/**
 * These are the fields for the Voting Machine Class.
 */
public class VotingMachine
{
    private ArrayList<String> candidateList;

    /**
     * The following constructor will establish the Candidate List
     */
    public VotingMachine()
    {
        candidateList = new ArrayList<String>();
    }

    /**
     * This constructor will store the Candidates for the Candidate List   
     */
    public void setCandidateList()
    {
        candidateList.add("Darnell Woffard");
        candidateList.add("Barack Obama");
        candidateList.add("Hillary Clinton");
    }    

    /**
     * This method will display the entire Candidate List.
     */
    public void printCandidateInfo()
    {
        for (int index=0; index < candidateList.size(); index++)
        {
            System.out.println(candidateList.get(index));
        }
    }

    /**
     * Method to the number of Candidates in the CandidateList Arraylist.
     */
    public int getNumberofFiles()
    {
        return candidateList.size();       
    }

   /**
    * Method to select one candidate by first providing an index number.
    */
   public void listFile(int index)
   {
       if(index >= 0 && index < candidateList.size()){
           String filename = candidateList.get(index);
           System.out.println(filename);
       }
   }

    /**
     * This method will enable a user to remove a candidate.
     */
    public void removeFile(int index)
    {
        if(index >= 0 && index < candidateList.size()){
            candidateList.remove(index);
        }
    }

    /**
     * This method will add a file to the Candidate List.
     * 
     */
    public void addCandidate(String filename)
    {
       candidateList.add(filename);
    }


//----------
//The Candidate Class:

public class Candidate{

    private String name;
    private char party;
    private String candidateList;
// Add fields
    /**
     * Fields
     * name - Candidate's name, stored in a String
     * party - Candidate's political party, stored in a char
     * as 'r' for Republican, 'd' for Democrat, and 'i' for Independent
     */

    /**
     * Constructor
     * 
     * @param anyName - caller inputs Candidate name
     * @param anyParty - caller inputs Candidate's party affiliation
     * stored as a char
     * chars are assigned with single quotes.
     */
    public Candidate(String anyName, char anyParty)
    {
        name = anyName;
        party = anyParty;   
    }

    /**
     * The method will enable method calls from the Voting Machine Class.
     */
    public void main(String candidateList)
    {
        VotingMachine votingMachine = new VotingMachine();
    }

            /**
             * This method will define the candidates party affiliation.
             * public char setParty()
             */


//Complete the three methods and their comments.    
    /**
     * Method to retrieve the Candidate's name for the caller.
     * public String getName(String anyName)
     * 
     */



    /**
     * Method to retrieve the Candidate's party for the caller.
     * 
     * @return
     */



    /**
     * Method to change the Candidate's party
     * 
     * @param 
     */

Answer 1

Actually what i got from this is you are trying to make a voting machine. VotingMachine is the main class here having info of different candidates. so we will make object of candidate in votingMachine class. Note: when we are supposed to make a java project, figure out what is it main class and subclass that means which depends on which. in the above example There is association in the classes. First of all declare an ArrayList for storing objects of candidate class. as shown below.

private ArrayList<candidate> candidateList;

/**
 * The following constructor will establish the Candidate List
 */
public VotingMachine()
{
    candidateList = new ArrayList<String>();
}

now for adding new candidate in the ArrayList I have modified your method setCandidate() as

public void addNewCandidate(String name, char partySymbol)
{
    candidate candid = new candidate(name, partySymbol);// this will call the candidate constructor
    candidateList.add(candid);//add that object in ArrayList


}    

As ArrayList stores references of objects, the built-in function int get(int index) will return the reference of the object. to print the info of that object or you can say values, we should define a function as getName() and getParty() . instead of this System.out.println(candidateList.get(index)); you should call System.out.println(candidateList.get(index).getName()); and System.out.println(candidateList.get(index).getParty()); in the following method

public void printCandidateInfo()
{
    for (int index=0; index < candidateList.size(); index++)
    {
        System.out.println(candidateList.get(index));
    }
}

so define functions in candidate class as

public String getName()
{
    return name;

}

/**
 * Method to retrieve the Candidate's party for the caller.
 * 
 * @return
 */
public char getParty()
{
    return party;

}

the following method will print the reference not the info of candidate, so modify it as described above

public void listFile(int index)
{
      if(index >= 0 && index < candidateList.size()){
       String filename = candidateList.get(index);
       System.out.println(filename);
   }

}

as i have modified it,

import java.util.ArrayList;

/**
* These are the fields for the Voting Machine Class.
*/

public class VotingMachine
{
private ArrayList<Candidate> candidateList;

/**
 * The following constructor will establish the Candidate List
 */
public VotingMachine()
{
    candidateList = new ArrayList<>();
}

/**
 * This method will store the Candidates for the Candidate List   
 */
public void addNewCandidate(String name, char partySymbol)
{
    Candidate candid = new Candidate(name, partySymbol);// this will call the candidate constructor
    candidateList.add(candid);//add that object in ArrayList
}    

/**
 * This method will display the entire Candidate List.
 */
public void printCandidateInfo()
{
    for (int index=0; index < candidateList.size(); index++)
    {
        System.out.print(candidateList.get(index).getName());
        System.out.println("  " + candidateList.get(index).getParty());
    }
}

/**
 * Method to the number of Candidates in the CandidateList Arraylist.
 */
public int getNumberofFiles()
{
    return candidateList.size();       
}

/**
* Method to select one candidate by first providing an index number.
*/
public void listFile(int index)
{
   System.out.print(candidateList.get(index).getName());
   System.out.println("  " + candidateList.get(index).getParty());
}

/**
 * This method will enable a user to remove a candidate.
 */
public void removeFile(int index)
{
    if(index >= 0 && index < candidateList.size()){
        candidateList.remove(index);
    }
}

}

in candidate class i have just added the above mentioned getName() and getParty() methods..

regards