What does early initialization of Singleton class in Java mean

Well, Lazy initializationmeans you don't initialize the object before it's first used.

Early initializationJust the opposite, you need to pre-initialize a singleton when loading the class.

There are many ways to do early initialization, one way is to declare a singleton as static.

Here is an example:

public class SingletonClassEarly {
    private static SingletonClassEarly sce = new SingletonClassEarly();
    private SingletonClassEarly() {} // make it private

    public static SingletonClassEarly getInstance() {
        return sce;
    }
}

According to the lifecycle, this singleton will be loaded after the JVM starts and when the class is initialized. On shutdown/exit it is unloaded by the JVM.