How is parseInt() different from valueOf() ?
They appear to do exactly the same thing to me (also goes for parseFloat(), parseDouble(), parseLong() etc, how are they different from Long.valueOf(string) ?
Also, which one of these is preferable and used more often by convention?
Well, the API for Integer.valueOf(String) does indeed say that the String is interpreted exactly as if it were given to Integer.parseInt(String). However, valueOf(String) returns a new Integer() object whereas parseInt(String) returns a primitive int.
If you want to enjoy the potential caching benefits of Integer.valueOf(int), you could also use this eyesore:
Integer k = Integer.valueOf(Integer.parseInt("123"))
Now, if what you want is the object and not the primitive, then using valueOf(String) may be more attractive than making a new object out of parseInt(String) because the former is consistently present across Integer, Long, Double, etc.