从字符串的 ArrayList 中删除数字

Question

I have ArrayList of Strings and I want to remove numbers from it. How Can achieve it?

ArrayList<String> arraylist = new ArrayList();

arraylist.add("01 Hello 88");
arraylist.add("02 World 88");

For example I just want to remove 01 and 02 .. and rest can be same

Answer 1

Seems like you want subString only since you want to remove only 01 not 88 then you can use substring()

for (int i = 0; i < arraylist.size(); i++) {
  arraylist.set(i, arraylist.get(i).substring(3));
}

Or You can use Stream API

List<String> arraylist = new ArrayList();
arraylist.add("01 Hello 88");
arraylist.add("02 World 88");
arraylist = arraylist.stream().map(a -> a.substring(3)).collect(Collectors.toList());

Answer 2

Interesting question. Here it is:

UnaryOperator<List<String>> trimHeader = (inList) -> {
    List<String> outList = new ArrayList<>();
    for (String s : inList) {
        String[] elements = s.split(" ");
        outList.add(Arrays.stream(elements).skip(1).collect(Collectors.joining(" ")));
    }
    return outList;
};

List<String> list = new ArrayList<>();
list.add("01 Hello 88");
list.add("02 World 88");
trimHeader.apply(list).forEach(System.out::println);

Output:

Hello 88
World 88

Notice that the Lambda function brings no side-effect to the original list.

[Edit] Updated a variable name above. In addition, consider the function provided in this reply for a more general purpose usage -- it removes the first element based on checking the space. The first element can be a number or some characters.

Answer 3

The easiest way to remove leading digits followed by spaces, is to use a regular expression to match that, and then replace it with an empty string.

The regex would be ^\\d+\\s+ , which as a Java string literal would be "^\\\\d+\\\\s+" .

To update all values in a list in Java 8+, you can do it using the replaceAll(UnaryOperator<E> operator) method, like this:

ArrayList<String> arraylist = new ArrayList<>();
arraylist.add("01 Hello 88");
arraylist.add("02 World 88");

arraylist.replaceAll(s -> s.replaceFirst("^\\d+\\s+", ""));

System.out.println(arraylist);

Output

[Hello 88, World 88]