关于单例模式的两个问题，请大虾帮忙！

[霸气正在侧漏]

1.
class S1 {
private S1() {
System.out.println("ok1");
}


private static S1 instance = new S1();

public static S1 getInstance() {
return instance;
}
}
S1是什么时候被创建？是在调用getInstance()时吗？

2.
class S4 {
private S4() {
System.out.println("ok4");
}

private static class S4Holder {
static S4 instance = new S4();
}


public static S4 getInstance() {
return S4Holder.instance;
}
}
这里，instance又是何时被创建？

[霸气正在侧漏]

没人回复，只能自顶