Java Undefined Object

By “undefined object as a parameter”, I assume you mean that you’re looking to write a function that doesn’t specify the type of the object in the function declaration, allowing you to only have one function.

This can be done with generics.

Instead of:

static void func(String str)
{
  System.out.println("The string is: "+str);
}
static void func(Integer integer)
{
  System.out.println("The integer is: "+integer);
}

you can have:

static <T> void func(T value)
{
  if (value instanceof Integer)
    System.out.println("The integer is: "+value);
  else if (value instanceof String)
    System.out.println("The string is: "+value);
  else
     System.out.println("Type not supported!! - "+value.getClass());
}

Test:

func("abc"); // The string is: abc
func(3);     // The integer is: 3
func(3.0);   // Type not supported!! - class java.lang.Double

See Java generics for more information.