How to write a generic method that takes two arguments of the same types in java?

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The reason that this compiles is because Java will infer the most specific supertype of the arguments passed in, in this case, Object Serializable & Comparable<? extends Serializable & Comparable<? extends Comparable<?>>>, after 1 is boxed to Integer and "1" is passed as a String.

Without generics:

private static void method(Number arg1, Number arg2) {

Even without generics, you can pass in an Integer and a Double.

Only if the type in question is final can you do this, without generics:

private static void method(String arg1, String arg2) {
    // Yes, they're both Strings, guaranteed.

There is one edge case with generics that I can think of to ensure that they are the exact type. If you have a final class, and you place an upper bound, then you can restrict it to that same class.

public <T extends MyFinalClass> void method(T arg1, T arg2) {
    // Yes, they're both MyFinalClasses
}

But then you could do the same thing without generics.

public void method(MyFinalClass arg1, MyFinalClass arg2) {
    // Yes, they're both MyFinalClasses
}

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