How does this not work? I need a hint...

Question about the task

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public class IMF {

    private static IMF imf;

    public static IMF getFund() {
        synchronized (imf) {
            if(imf == null)
                imf = new IMF();
        return imf;
        }
    }

    private IMF() {
    }
}

Singleton pattern: synchronization in a method.
The IMF class is the International Monetary Fund.
Create a synchronized block inside the getFund method.
Inside the synchronized block, initialize imf so that the getFund method always returns the same object.

Requirements:

The IMF class must have a private static IMF field imf.
The IMF class must have a private constructor.
The IMF class must have a public static IMF getFund() method.
The getFund() method must have a synchronized block.
The synchronized block must initialize imf.
The getFund() method must always return the same object.

package com.codegym.task.task17.task1707; /* IMF */ public class Solution { public static void main(String[] args) { IMF fund = IMF.getFund(); IMF anotherFund = IMF.getFund(); System.out.println(fund == anotherFund ); } }

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Philip T-D

Level 18 , San Diego, United States

2 May 2019, 17:17

solution

synchronized (IMF.class) {
    if(imf == null)
        imf = new IMF();
return imf;
}

+17

Philip T-D

Level 18 , San Diego, United States

2 May 2019, 17:17

This was the solution... Tho can't say I understand why. Any guidance / articles to enlighten me are appreciated!

Ed Maphis

Level 20 , Painesville, United States

14 June 2019, 18:55

Google: synchronized singleton pattern.

Pandora

Level 17 , Stockholm, Sweden

23 March 2020, 09:37

Thank you for the link!

Roman Grygorczuk

Level 19 , Cracow, Poland

20 February 2021, 19:32

https://medium.com/swlh/java-singleton-pattern-and-synchronization-32665cbf6ad7