code: public static Optional<Number> abs( Object arg ) {
          if(arg instanceof Integer) {
              return Optional.<Number>of( java.lang.Math.abs( (Integer) arg ));
          }
          else if(arg instanceof Double) {
              return Optional.<Number>of( java.lang.Math.abs( (Double) arg ));
          }
          else if(arg instanceof Long) {
              return Optional.<Number>of( java.lang.Math.abs( (Long) arg ));
          }
          else if(arg instanceof String) {
              return abs( Objects.toNumber( arg ).get() );
          }
          return Optional.empty();
      }
docs: Given any object, returns, if possible. its absolute value wrapped in Optional
  Interprets String as Number
  
  abs("-123") == Optional.of(123)
  abs("123") == Optional.of(123)
  abs("12.3") == Optional.of(12.3)
  
  abs("abc") == Optional.empty()
  abs(null) == Optional.empty()