[FIXED] Trying to access an ArrayList from another class

Issue

Hi guys im kind of new in Java and I am trying to clone a arrayList into another ArrayList that resides in another class, here's the code of the original ArrayList in my TaskPage.java:

public ArrayList<String> tName = new ArrayList<>();
    public ArrayList<String> tDesc = new ArrayList<>();
    public ArrayList<String> fLName = new ArrayList<>();
    public ArrayList<String> tStatus = new ArrayList<>();
    public ArrayList<Integer> tDuration = new ArrayList<>();
    public ArrayList<String> tID = new ArrayList<>();    

String TName = taskName.getText();
        tName.add(TName);
        String TDescription = taskDescription.getText();
        tDesc.add(TDescription);
        String FName = FirstName.getText();
        String LName = LastName.getText();
        fLName.add(FName + " " + LName);
        int Duration = Integer.parseInt(taskDuration.getText());
        tDuration.add(Duration);
        String taskID;
       
        String taskNumber = "";
        Random rand = new Random();
        
        int rNum = rand.nextInt(21);
        
        taskNumber = "0" + Integer.toString(rNum);
        
        TaskClass tClass = new TaskClass();
        taskID = tClass.createTaskID(TName, taskNumber, FName);
        tID.add(taskID);

here is the code for Report.java:

public class Report {
    TaskPage tPage = new TaskPage();
    public ArrayList<String> taskName;
    public ArrayList<String>  taskDesc;
    public ArrayList<String>  fLName;
    public ArrayList<String>  taskStatus;
    public ArrayList<String>  taskDuration;
    public ArrayList<String>  taskID;
    
    public String res = "";
    
    public void init() {
        taskName = (ArrayList)tPage.tName.clone();
    taskDesc = (ArrayList)tPage.tDesc.clone();
     fLName = (ArrayList)tPage.fLName.clone();
     taskStatus = (ArrayList)tPage.tStatus.clone();
     taskDuration = (ArrayList)tPage.tDuration.clone();
        taskID = (ArrayList)tPage.tID.clone();
    }
    
    public void statusDone() {
        init();
        for (int k=0; k <= tPage.tName.size(); k++) {
            if (tPage.tStatus.get(k) == "Done") {
                res = tPage.fLName.get(k) + ", " + tPage.tName.get(k) + ", " + tPage.tDuration.get(k) + "\n";
            } else {
                res = "There is nothing to display here!";
            }
        }
    }
}

And lastly here is the code for my ComingSoon.java:

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
        Report rpt = new Report();
        rpt.statusDone();
        String Status = rpt.res;
        JOptionPane.showMessageDialog(null, Status);
    }

When I run the code it gives the error:

Exception in thread "AWT-EventQueue-0" java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
    at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64)
    at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70)
    at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:266)
    at java.base/java.util.Objects.checkIndex(Objects.java:359)
    at java.base/java.util.ArrayList.get(ArrayList.java:427)
    at userlogin.Report.statusDone(Report.java:36)
    at userlogin.ComingSoon.jButton1ActionPerformed(ComingSoon.java:188)
    at userlogin.ComingSoon$1.actionPerformed(ComingSoon.java:54)
    at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1972)
    at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2313)
    at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405)
    at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262)
    at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:279)
    at java.desktop/java.awt.Component.processMouseEvent(Component.java:6626)
    at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3389)
    at java.desktop/java.awt.Component.processEvent(Component.java:6391)
    at java.desktop/java.awt.Container.processEvent(Container.java:2266)
    at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:5001)
    at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2324)
    at java.desktop/java.awt.Component.dispatchEvent(Component.java:4833)
    at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4948)
    at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4575)
    at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4516)
    at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2310)
    at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2780)
    at java.desktop/java.awt.Component.dispatchEvent(Component.java:4833)
    at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:773)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:722)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:716)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:97)
    at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:746)
    at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:744)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
    at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:743)
    at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

Solution

There are a number of problems in your code, but the reason you get an ArrayIndexOutOfBoundsException is that the for loop in the statusDone() function is wrong.

for (int k=0; k <= tPage.tName.size(); k++) {
    ...

The problem occurs when k = tPage.tName.size().

Since arrays (and ArrayLists) are 0 indexed, the element at k-1 is the last element, so tPage.tStatus.get(k) throws an ArrayIndexOutOfBoundsException. You should use < instead of <=.

---

Another possible problem is that you don't seem to call init() anywhere. I assume that init() should be called before statusDone().

Additional suggestions for better readability and maintainability:

• Instead of having 6 ArrayLists of strings, make a Task class that has 6 fields, and replace the 6 lists with ArrayList<Task> (thanks Dave Newton)

• Use new ArrayList<>(tPage.tName) instead of (ArrayList)tPage.tName.clone(). Using clone() on collections is usually discouraged, and casting it is also not very clean.

• Consider moving everything from init() to the constructor. That way, you don't have to remember to call init(); the code just gets run when you call new Report()

Answered By - Jay Ren
Answer Checked By - Clifford M. (JavaFixing Volunteer)