Here I am giving two reasons ----

1. Java supports primitive datatypes like byte,int,char, float,double etc.. In
the case of these primitive datatypes we don't need to creat any object of their
respective classes (e.g Integer,Float,Double etc), we can directly use int x = 0
; float y= 0.0f ; etc. So this goes against the concept of "encapsulation" which
is one of the basic features of OOPS.

2. Java does not support multiple inheritence.