EJB 面试题与答案

Question: What is lazy loading?

Answer: Lazy loading means not creating an object until the first time it is accessed. Lazy loading typically looks like this:

public class Example {
private Vector data = null;
public Vector getData() {
if (this.data == null) {
this.data = new Vector();
// Load data into vector �
}
return this.data;
}
}

This technique is most useful when you have large hierarchies of objects (such as a product catalog). You can lazy-load subordinate objects as you navigate down the hierarchy, and thereby only create objects when you need them.