java generics: can't create a simple print array method

问题

So i keep on getting an error on the next code. And I have no idea what i'm doing wrong. The error is The method printArray(T[]) in the type main is not applicable for the arguments (int[])

public class main {

    public static void main(String[] args) {
        Oefening1 oef = new Oefening1();
        int[] integerArray = {1,2,3,4,5};
        printArray(integerArray);
    }

    public static <T> void printArray(T[] arr){
        for(T t: arr){
           System.out.print(t + " ");
        }
        System.out.println("");
    }

}

回答1:

When it comes to generics, Java makes a difference between primitive types and types derived from java.lang.Object. Only non-primitive types can be used as arguments of generic methods. Since int is not generic, printArray<T> does not apply to it.

You can fix it by providing an overload for int, or by making integerArray an Integer[]:

Integer[] integerArray = {1,2,3,4,5};
printArray(integerArray);

Demo.

The reason this works is that Integer wraps int in an object suitable for passing to generics. However, this takes a lot of help from Java compiler, because when you write {1,2,3,4,5} it gets translated to {Integer.valueOf(1), Integer.valueOf(2), Integer.valueOf(3), Integer.valueOf(4), Integer.valueOf(5)} behind the scene.

回答2:

Its because you are using primitive type of the data type. If you use Integer[] integerArray = {1,2,3,4,5}; instead of int[] integerArray = {1,2,3,4,5};. It should work.

来源：https://stackoverflow.com/questions/27706282/java-generics-cant-create-a-simple-print-array-method