无法在方法括号内放置新的列表

Question

Senario:

So I am trying to simplify the usage of setting a lot of TextViews invisible by making a lot a lines of code into one, so decided to make a method that gets List<TextView> and turns them all invisible. I made a test Class to show the error. (Problem bellow)

Method:

 private void makeTextViewsInvisible(List<TextView> listOfTextViews){
    int i= 0;
    while(i < listOfTextViews.size()){
        listOfTextViews.get(i).setVisibility(View.INVISIBLE);
        i++;
    }
}

Using the method:

makeTextViewsInvisible(new List<t1,t2,t3>()) ;
            //Dose'nt work?
            //I don't want to define : (List<TextView> a  = new ...) And add TextViews manually (a.add(TextView1)...)
            //I want to add all three TextViews in one line of code inside the brackets

Problem is, that I cannot make a new List inside the brackets, I need to make a whole new List and add all the TextViews manually (By using List.add(); ), witch dosent simplify my code. Any way to make a new List inside the bracket it self?

Answer 1

The syntax

makeTextViewsInvisible(new List())

is incorrect. You clearly do not understand the syntax of List initialization. If you want to insert three elements to the list of a given type (in your case it'll be List<TextViews> I believe) you have to initialize it (the list of type TextViews ). Note that you probably don't want to instantiate a List, because it is an interface and you would have to implement every method of List interface, such as add(), get(), indexOf() etc. I suggest that you pass the ArrayList as your function argument. Let's say that t1,t2,t3 are already defined objects of type TextViews . To instantiate ArrayList<TextViews> you need the following syntax:

ArrayList<TextViews> exampleList= new ArrayList<>(Arrays.asList(t1,t2,t3));

You have to pass an array as a constructor of a list, which you can easily do with Arrays.asList() static method. With that said, syntax of your method invocation would look like this:

makeTextViewsInvisible(new ArrayList<TextViews>(Arrays.asList(t1,t2,t3));

Answer 2

You could do something like that if you would use this library...
org.apache.commons

Then it should be possible to call your method like this.

List<String> newList = ListUtils.union(list1,list2);


makeTextViewsInvisible(ListUtils.union(t1,t2,t3));