title: what is the use of Abstract modifier with primitive data type in java?
body: <p>What is use of <code>abstract</code> modifier with primitive data type? In <code>java.io.Reader class,read(char[] cbuf, int off, int len)</code> return type is "abstract int".
  Can we use only "int" instead of "abstract int" or not?
  What is the diffrence between these two?</p>