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Question about the task

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println mehtod is unable to acess the note variable but why ?

1. The Note class will be used by threads. So be sure that attempts to access the notes list lock notes, not this
2. Calls to System.out.println must not be synchronized, i.e. must not be in the synchronized block

Requirements:

The addNote() method should add notes to the notes list.
The removeNote() method must delete a note from the notes list.
The addNote() method must have a synchronized block.
The removeNote() method must have a synchronized block.
The synchronized block in the addNote() method must lock notes.
The synchronized block in the removeNote() method must lock notes.
The addNote() method's synchronized block must call the add method on notes.
The removeNote() method's synchronized block must call the remove method on notes.
No screen output commands should be in the synchronized block.

package com.codegym.task.task17.task1703; import java.util.ArrayList; import java.util.List; /* Synchronized notes */ public class Solution { public static void main(String[] args) { } public static class Note { public final List<String> notes = new ArrayList<>(); public void addNote(int index, String note) { System.out.println("A note [" + note + "] will now be added at position " + index); synchronized (notes) { notes.add(index, note); } System.out.println("The note [" + note + "] has already been added"); } public void removeNote(int index) { System.out.println("A note will now be deleted from position " + index); synchronized (notes) { String note = notes.remove(index); } System.out.println("The note [" + note + "] has already been deleted from position " + index); } } }

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hanumohan

Level 25 , San Jose, United States

3 May 2020, 21:28

synchronized(notes) {
                notes.add(index, note);
            }
            System.out.println("A note [" + note + "] will now be added at position " + index);

            System.out.println("The note [" + note + "] has already been added");
        }

        public void  removeNote(int index) {

            synchronized (notes){
//                notes.remove(index);
            }
            System.out.println("A note will now be deleted from position " + index);

            String note = notes.remove(index) ;
            System.out.println("The note [" + note + "] has already been deleted from position " + index);
        }

Ntuthuko Xaba

Level 18 , Johannesburg, South Africa

28 April 2020, 21:23

The 'note' in line 32 and the 'note' in line 34 , need to be the same , so declare a 'note' variable that will be available for use in the entire method , and remove the String declaration in line 32.

Nouser

Level 36 , Germany

28 April 2020, 18:28

the lifetime of String note = ... is only within the synchronized block and maybe it helps to reset the task