How to split strings of list into string array

I have a list that contains ("One.two.three", "one.two.four"). I want to save then in a string array as

One
two
three
one
two
four

What is the logic behind it?

You should be using java 8 to run this code. Just take those strings and split them on "."
split method of java need regex so to match "." you need "\.".Then transform array to list, then add words to list.

public static void main(String[] args) {
		List<String> words = new ArrayList<String>();
		List<String> list = new ArrayList<String>();
		list.add("One.two.three");
		list.add("one.two.four");
		list.stream().forEach(str -> {
			words.addAll(Arrays.asList(str.split("\\.")));
		});
		System.out.println(words.toString());
        //output : [One, two, three, one, two, four]
	}

For java 8+, you can use flatmap as -

String[] words = list.stream().flatMap(str -> Arrays.stream(str.split("\\."))).toArray(String[]::new);

If you are talking about the static arrays it is important to know array size to avoid "index is out of bounds" exception.

This way, I provide the solution that counts the number of words and then creates output s array to save every word.

We can use the String.split() function to get the single words we adding to output array:

String[] a = {"One.two.three", "one.two.four"};
int count = 0;
for (int i = 0; i < a.length; i++) { //skip this loop if you know the wanted array size
    count += a[i].split("\\.").length;
}
String[] s = new String[count];
int k = 0;
for (int i = 0; i < a.length; i++) {
    String[] b = a[i].split("\\.");
    for (int j = 0; j < b.length; j++) {
        s[k++] = b[j];
    }
}
for (int i = 0; i < s.length; i++) {
    System.out.println(s[i]);
}

Try this.

FOR JAVA 1.8+

public static void main(String[] args) {
List<String> list = new ArrayList<String>();
list.add("One.two.three");
list.add("One.two.four");
List<String> newList = new ArrayList<String>();
list.forEach(string -> {
String[] stringArr = string.split("\\.");
for (String innerString : stringArr) {
newList.add(innerString);
} 
});
String[] stringArr = newList.toArray(new String[newList.size()]);
System.out.println(Arrays.toString(stringArr));
}

UPTO JAVA 1.7

public static void main(String[] args) {
List<String> list = new ArrayList<String>();
list.add("One.two.three");
list.add("One.two.four");
List<String> newList = new ArrayList<String>();
for (String string : list) {
String[] stringArr = string.split("\\.");
for (String innerString : stringArr) {
newList.add(innerString);
} 
}
String[] stringArr = newList.toArray(new String[newList.size()]);
System.out.println(Arrays.toString(stringArr));
}

If you are below Java 8 you can use this snippet:

public class Main {
public static void main(String[] args) throws Exception {
List<String> originalList = new ArrayList();
List<String> finalList = new ArrayList();
originalList.add("One.two.three");
originalList.add("One.two.four");
for(String myString : originalList) {
//The \\ is to scape the dot
finalList.addAll(Arrays.asList(myString.split("\\.")));
}
//Creates an array from the list
String[] theArray = finalList.toArray(new String[finalList.size()]);
}
}

Finally, theArray will contain:

[One, two, three, one, two, four]

Take a look at the docs about splitting an string into parts