Add multiple String variables to ArrayList

Question

Suppose I have a lot of String Variables(100 for example):

   String str1 = \"abc\";
    String str2 = \"123\";
    String str3 = \"aaa\";
....
    String st         


        

Answer 1

Yes. The way to use a loop is not to declare 100 string variables. Use one array instead.

String[] str = new String[101];
str[1] = "abc";
str[2] = "123";
str[3] = "aaa";
....
str[100] = "zzz";

(I made the indexes go from 1 to 100 to show how it corresponds to your original code, but it's more normal to go from 0 to 99 instead, and to initialize it with an array initializer as in @markspace's answer.)

Answer 2

The following creates the ArrayList on the specific String values you have:

ArrayList<String> list1 = new ArrayList<String>() {{addAll(Arrays.asList(new String[]{"99", "bb", "zz"}));}};

Or, if it's just some distinct values you want, use this for say - 10 of them:

ArrayList<String> list2 = new ArrayList<String>() {{for (int i=0; i<10; i++) add(""+System.currentTimeMillis());}};

Answer 3

Use an array:

String[] strs = { "abc","123","zzz" };

for(int i =  0; i < strs.length; i++){
     list.add(strs[i]);  //something like this?
}

This idea is so popular that there's built-in methods to do it. For example:

  list.addAll( Arrays.asList(strs) );

will add your array elements to an existing list. If you just want a list with only the array elements, you can do it on one line:

  List<String> list = Arrays.asList( strs );

Answer 4

If strX would be class fields then you could try using reflection - link to example of accessing fields and methods.

If it is local variable then you can't get access to its name so you will not be able to do it (unless str would be array, so you could access its values via str[i] but then you probably wouldn't need ArrayList).

Update:

After you updated question and showed that you have 100 variables

String str1 = "abc";
String str2 = "123";
String str3 = "aaa";
//...
String str100 = "zzz";

I must say that you need array. Arrays ware introduced to programming languages precisely to avoid situation you are in now. So instead of declaring 100 separate variables you should use

String[] str = {"abc", "123", "aaa", ... , "zzz"};

and then access values via str[index] where index is value between 0 and size of your array -1, which in you case would be range 0 - 99.

---

If you would still would need to put all array elements to list you could use

List<String> elements = new ArrayList<>(Arrays.asList(str));

which would first

Arrays.asList(str)

create list backed up by str array (this means that if you do any changes to array it will be reflected in list, and vice-versa, changes done to list from this method would affect str array).

To avoid making list dependant on state of array we can create separate list which would copy elements from earlier list to its own array. We can simply do it by using constructor

new ArrayList<>(Arrays.asList(str));

or we can separate these steps more with

List<String> elements = new ArrayList<>();//empty list
elements.addAll(Arrays.asList(str));//copy all elements from one list to another

Answer 5

If you want to stick to good practice, declare your Strings in an array:

String[] strs = new String[]{ "abc", "123", "aaa", ... };
for (String s : strs) // Goes through all entries of strs in ascending index order (foreach over array)
    list.add(s);

Answer 6

If you are using Java 9 then easily you can add the multiple String Objects into Array List Like

List<String> strings = List.of("abc","123","zzz");