How do I use getClass() to tell if an Object is numeric?

Question

I want to dynamically tell if an Object in Java is numeric or not. My code is as the following:

if(obj.getClass().equals(Number.class)) {
    attributeTypeStr = "Numeric";
} else {
    attributeTypeStr = "Non-Numeric";
}

The Object obj can be any numeric types like Integer, Float, Double, etc. But when I tested it with Integer/Float/Double, the attributeTypeStr always returns "Non-Numeric". I guess that's because Integer/Float/Double are subclasses of Number but Number.class does not equal Double.class. I could use something like

if(obj.getClass().equals(Integer.class) || obj.getClass().equals(Float.class) || obj.getClass().equals(Double.class))

But it looks too verbose. So is there a simple way to do that?

Answer 1

Use instanceof:

if (obj instanceof Number)

Answer 2

Use Class#isAssignableFrom(Class) which states

Determines if the class or interface represented by this Class object is either the same as, or is a superclass or superinterface of, the class or interface represented by the specified Class parameter.

Doing

Integer obj = new Integer(2);       
System.out.println(Number.class.isAssignableFrom(obj.getClass()));

will therefore print true.

It might not be relevant to your question, but just fyi:

• What is the difference between instanceof and Class.isAssignableFrom(…)?

Answer 3

Use isInstance() method of Class

if(Number.class.isInstance(obj)){
}

According to Class#isInstance()

Determines if the specified Object is assignment-compatible with the object represented by this Class. This method is the dynamic equivalent of the Java language instanceof operator. The method returns true if the specified Object argument is non-null and can be cast to the reference type represented by this Class object without raising a ClassCastException. It returns false otherwise.

Answer 4

Check its superclass. This works as these classes are direct superclasses:

if(obj.getClass().getSuperclass().equals(Number.class)){
    //logic
}

Or for non-direct, check Number.class.isAssignableFrom(obj.getClass()). For numeric, it shouldn't be very much of a problem as the existing Number subclasses are final. In gnerics, this may break due to the absence of type information.