Java Data Type How to - Check if a string represent a float number

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Question

We would like to know how to check if a string represent a float number.

Answer

public class Main {
/*from   w w w  .ja  va 2s  . c om*/
  public static void main(String[] args) {
    System.out.println(testNumber("2.2"));
  }

  public static Float testNumber(String aArg) {
    while (true) {
      if (aArg.length() == 0) {
        return null;
      }
      if (aArg.matches("-?\\d+(\\.\\d+)?") == true) {
        break;
      } else {
        throw new IllegalArgumentException("not a number");
      }
    }
    return Float.parseFloat(aArg);
  }
}

The code above generates the following result.

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