how to extract numeric values from input string in java

Question

How can I extract only the numeric values from the input string?

For example, the input string may be like this:

String str=\"abc d 1234567890pqr 548         


        

Answer 1

public static List<String> extractNumbers(String string) {
    List<String> numbers = new LinkedList<String>();
    char[] array = string.toCharArray();
    Stack<Character> stack = new Stack<Character>();

    for (int i = 0; i < array.length; i++) {
        if (Character.isDigit(array[i])) {
            stack.push(array[i]);
        } else if (!stack.isEmpty()) {
            String number = getStackContent(stack);
            stack.clear();
            numbers.add(number);
        }
    }
    if(!stack.isEmpty()){
        String number = getStackContent(stack);
        numbers.add(number);            
    }
    return numbers;
}

private static String getStackContent(Stack<Character> stack) {
    StringBuilder sb = new StringBuilder();
    Enumeration<Character> elements = stack.elements();
    while (elements.hasMoreElements()) {
        sb.append(elements.nextElement());
    }
    return sb.toString();
}

public static void main(String[] args) {
    String str = " abc d 1234567890pqr 54897";
    List<String> extractNumbers = extractNumbers(str);
    for (String number : extractNumbers) {
        System.out.println(number);
    }
}

Answer 2

You could do something like:

Matcher m = Pattern.compile("\\d+").matcher(str);
while (m.find()) {
   System.out.println(m.group(0));
}

Answer 3

You want to discard everything except digits and spaces:

String nums = input.replaceAll("[^0-9 ]", "").replaceAll(" +", " ").trim();

The extra calls clean up doubled and leading/trailing spaces.

If you need an array, add a split:

String[] nums = input.replaceAll("[^0-9 ]", "").trim().split(" +");