Write a thread safe singleton in Java

Question

Given this code
```java
public class Singleton {

public static Singleton getInstance() {
    return SingletonHolder.instance;
  }

private static class SingletonHolder {
    private static final Singleton instance = new Singleton();
  }
}
```

What assertions are true?

Accepted Answer

Is ThreadSafe and non blocking

Accepted Answer

Would not behave the same way by declaring `instance` directly in `Singleton`

Accepted Answer

The singleton is instanciated upon first call

Answer

The singleton is instanciated with the JVM start

Question from the Java and Craftsmanship test