从另一个类访问arraylist

Question

I am a newbie to Java and I have a gui class which has a GUI component and it takes the input from the text field and should pass it to another class. The action listener of the button is below.

public void actionPerformed(ActionEvent action) {               
  arraylist.add(textField_1.getText());
  arraylist.add(textField_2.getText());
  arraylist.add(textField_3.getText());
  arraylist.add(textField_4.getText());     
}

since it is a void method I cannot return the array list so that Ii cannot construct a getter.

public ArrayList<String> getList(){
    return this.arraylist;
}

Could anyone please tell me how to access this arraylist from the another class without passing it through the constructor? I am sorry if i asked anything wrong. Thanks in advance.

Answer 1

This is one of the many possible approaches.

Just define another class and call the setter from your actionPerformed(..) method.

public class YourOtherClass {
    private static ArrayList<String> arraylist;

    public void setList(arrayList) {
        this.arraylist = arraylist;
    }

    public ArrayList<String> getList() {
        return this.arraylist;
    }
}

Now you can simply set this arraylist as:

public void actionPerformed(ActionEvent action) {               
    arraylist.add(textField_1.getText());
    arraylist.add(textField_2.getText());
    arraylist.add(textField_3.getText());
    arraylist.add(textField_4.getText());     
    YourOtherClass.setList(arraylist);
}

Now when you want to access the contents of this list, simply use:

...
//any other method
ArrayList<String> arraylist = YourOtherClass.getList();
System.out.println(arraylist.get(0)); //or whatever
...

Answer 2

If I understood, you want to do it:

public class A {
    private ArrayList<String> arrayList;

    public ArrayList<String> getArrayList() {
        return this.arrayList;
    }
}


public class B {
    private A a = new A();

    public void actionPerformed(ActionEvent action) {               
        a.getArrayList().add(textField_1.getText());
        a.getArrayList().add(textField_2.getText());
        a.getArrayList().add(textField_3.getText());
        a.getArrayList().add(textField_4.getText());     
    }
}

Answer 3

You can make that arraylist as Static and access it.

To access that particular arraylist use the below syntax

classNameThatContainArraylist.yourArrayList

be careful while using static.

Answer 4

If you want to use to set and get data then there are many approaches and two of them are follow

 public class SetDataInArrayList {

//Aproach one by using object
        private List<ActionEvent> list;
public SetDataInArrayList() {
        list = new ArrayList();
    }

    public void setDataInList(ActionEvent e) {
        list.add(e);
    }

    public List<ActionEvent> getList() {
        return list;
    }

//Approach two by using static reference
private static List<ActionEvent> newList;

    static {
        newList = new ArrayList<>();
    }

    public static void add(ActionEvent e) {
        newList.add(e);
    }

    public static List<ActionEvent> returnList() {
        return newList;
    }

if you use either of approach you will need reference variable in both of cases to fetch data