java - Benefits of Private Constructor - Singleton Design Pattern

Question

I understand that it helps creates single copy of class.

I would like to know:

1. What is the harm in creating multiple such instances of a class ? since garbage collection will take care of it.
2. Is it that it helps when multiple classes/threads use it and Java may run out of memory ?
3. It helps avoiding memory leak ?
4. How to decide if singleton pattern is better for me use case ?

Or could you please lead me to resources that can be helpful to learn more about it.

Thanks

Answer 1

看到这些，

设计模式：单例模式，优缺点

单例模式——积极和消极方面

辛格尔顿