Access ArrayList from another class

 

 

 

When ArrayList is needed from another class, use get/set method to return the list

다른 class에 있는 ArrayList를 사용하고 싶을 때는 get/set 메서드를 이용해서 불러오면 된다.

 

 

 

Example code I

 

class 1

import java.util.ArrayList;
import java.util.Iterator;
 
public class Main {
 
    public static void main(String[] args) {
        AnotherClass anotherClass = new AnotherClass();
 
        anotherClass.addList();
        ArrayList<Integer> list = anotherClass.getList();
 
        Iterator<Integer> itr = list.iterator();
 
        while (itr.hasNext()) {
            Integer i = itr.next();
            System.out.print(i + ", "); //1, 2, 3, 4,
        }
    }
}

 

class 2

import java.util.ArrayList;
 
public class AnotherClass {
 
    ArrayList<Integer> list = new ArrayList<>();
 
    public void addList() {
        list.add(1);
        list.add(2);
        list.add(3);
        list.add(4);
    }
 
    //setter
    public void setList(ArrayList list) {
        this.list = list;
    }
 
    //getter
    public ArrayList getList() {
        return list;
    }
}

 

 

*static으로 선언하고 사용할 수도 있지만 너무 심한 static method는 oop과 반대되기에 지양되어야 한다. 

 

 

 

 

 

 

Example code II

 

The code below reads a CSV file and prints ArrayList from another class 

CSV file 을 읽어서 ArrayList에 저장한 다음에 Main class에서 저장한 list를 출력하는 예제

 

//CSV File
Id,name,phone,email,account_num,address
1,Mr. D,345-234-2346,tomo@gmail.com,94837,Toronto CA
2,Mrs. P,847-835-3343,summer@gmail.com,98427,Vancouver CA
3,Mrs. C,938-656-6640,siw0911@yahoo.com,93247,Alberta CA
4,Mr. S,324-345-5531,suh@gmail.com,93442,Toronto CA
 
//Main class
public class Main {
 
    public static void main(String[] args) {
        CustomManager manager = CustomManager.createCustomManager();
 
        try {
            manager.readFile("customList.csv");
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
 
        /////////////// 다른 class 에서 data 가지고 오기 //////////////////////
        ArrayList<CustomInfo> list = manager.getList();
        System.out.println(list.get(0)); //1,Mr. D,345-234-2346,tomo@gmail.com,94837,Toronto CA
    }
}
 
//Another Class
package customList;
 
import java.io.BufferedReader;
import java.io.*;
import java.util.ArrayList;
 
public class CustomManager {
    //ArrayList
    ArrayList<CustomInfo> customManagers = new ArrayList<>();
 
    //Singleton pattern
    static CustomManager inst = null;
    private CustomManager(){}
    public static CustomManager createCustomManager(){
        if(inst == null)
            inst = new CustomManager();
        return inst;
    }
 
    public void readFile(String csv) throws FileNotFoundException {
        BufferedReader csvFile = new BufferedReader(new FileReader("src" + File.separator + csv));
 
        try {
            String file = csvFile.readLine(); //to skip the first line
 
            while((file = csvFile.readLine()) != null){
                String[] data = file.split(",");
                //adding to ArrayList
                customManagers.add(new CustomInfo(Integer.parseInt(data[0]),data[1],data[2],data[3],data[4],data[5]));
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
 
        for (CustomInfo c : customManagers) {
            System.out.println(c.toString());
        }
    }
 
    public ArrayList<CustomInfo> getList(){
       return customManagers;
    }
}

 

 

 

 

 

Reference

https://stackoverflow.com/questions/39989988/access-arraylist-from-another-class