I use Generics, but not this class <T> thing!

Question

I am trying to call this method to combine two arrays using Google Collections

public static <T> T[] concat(T[] first,
                             T[] second,
                             Class<T> type)

It returns empty results. I use

ObjectArrays.concat(array1, array2, Blah.class)

which compiles only.

array1and array2have a type Blah[].

What is the correct syntax?

Bonus question: Do other collection libraries have documentation with examples?

Edit: The problem was in my bone code.

public void register(ButtonPair[] pairs) {
    pairs = ObjectArrays.concat(this.pairs, pairs, ButtonPair.class);
}

the right side of the thing is fine, but the left side does not designate this.pairsdue to ambiguity. Sorry And the hats go to Google Collections!

Answer 1

:

String[] arr1 = { "abc", "def" };
String[] arr2 = { "ghi", "jkl" };
String[] result = ObjectArrays.concat(arr1, arr2, String.class);

concat()?

Answer 2

Google Collections, unit tests.

:

String[] result = ObjectArrays.concat(
    new String[] { "a", "b" }, new String[] { "c", "d" }, String.class);
assertEquals(String[].class, result.getClass());
assertContentsInOrder(Arrays.asList(result), "a", "b", "c", "d");

, Class<T>, , , .

Answer 3

. , . 100% ? :

import com.google.common.collect.ObjectArrays;

public class ObjectArrayTest
{
    public static void main(String[] args)
    {
        String[] first = new String[] { "Fire", "Earth" };
        String[] second = new String[] { "Water", "Air" };

        String[] result = ObjectArrays.concat(first, second, String.class);

        for (String s : result)
        {
            System.out.println (s);
        }
    }
}

Answer 4

, , .

:

public void register(ButtonPair[] pairs) {
    pairs = ObjectArrays.concat(this.pairs, pairs, ButtonPair.class);
    }

public void register(ButtonPair[] pairs) {
    this.pairs = ObjectArrays.concat(this.pairs, pairs, ButtonPair.class);
    }

By the way, that’s why in our store we have a different naming convention for method parameters and variables than for instance variables (although not a terrible prefix / suffix for instance variables, for example _someInstanceVar).