Java Data Type - 如何判断是一个浮点数而不是一个数字

public class Main {

  public static void main(String[] args) {
    float f = (float) Math.sqrt(-10);
    boolean b1 = Float.isNaN(f);
    System.out.println(b1);

    Float fObj = new Float(f);
    boolean b2 = fObj.isNaN();
    System.out.println(b2);
  }
}