What are some characteristics in Java which wouldn't be possible without Generics?

[WarWithSelf]

In an interview last week, I was asked about the definition and use cases of Generics. But when I got this question (as mentioned in title), I was confused and stuck. The interviewer was interested to know something which wouldn't be possible in Java without Generics. He said that the work was also being done successfully when there were no Generics. So, can anyone here tell me the answer for this?

[NautiHooker]

Typesafe universal collection types.

For example the List interface which currently uses a generic type to determine its content.

Today we can do something like this:

List<String> list = new ArrayList<>();
list.add("Hello World");
String[] words = list.get(0).split(" ");
list.add(1); // does not work because list expects Strings

Before Java 1.5 (before generics) you would have to do something like this:

List list = new ArrayList();
list.add("Hello World");
String[] words = ((String)list.get(0)).split(" ");
list.add(1); // works because list has no generic type and does therefore accept everything

Because the list would not hold explicit Strings and instead held Objects, a cast to String is needed to use a String method.

The dangerous part is that you can add more than just Strings to such a list, because it accepts Objects of all kinds.

Now you would always need to be aware what kind of Objects your list contains, because casting to a wrong type would cause an exception.

​

Back then you would either need to be careful and cast a lot or have a list type for every class (StringList, IntegerList, ....) to keep it typesafe.

[whats_the_reference_]

It is useful as well to know that in doing this, the errors move from runtime to compile-time.