Boldface = additions to the bare parser.

/* TreeReadWrite.java: read and write binary trees
 * grammar for binary tree representation:
 *   bintree --->  tree '#'
 *   tree ---> '0' | '(' letter tree tree ')'
 *   letter ---> 'a' | 'b' | 'c' | ...
 */
public class TreeReadWrite {
   private char next; // holds next input char
   
   private class tnode { // typical binary tree node
      char ch;
      tnode left;
      tnode right;
   };

   private GetNext getNext = new GetNext();
   
   private void bintree() { // binary tree, ends with #
      scan();
      tnode root = tree();
      if (next != '#') error(1);
      treePrint(root);
      System.out.println("#");
   }
   
   private tnode tree() {
      tnode p;
      if (next == '0') {
         scan();
         p = null;
      }
      else {
         p = new tnode();
         if (next == '(')
            scan();
         else error(2);
         if (Character.isLetter(next)) {
            p.ch = next;
            scan();
         }
         else error(3);
         p.left  = tree();
         p.right = tree();
         if (next == ')')
            scan();
         else error(4);
      }
      return p;
   }

   private void scan() { // next char, ignore whitespace
      while (Character.isWhitespace(next = getNext.getNextChar()))
         ;
   }

   private void error(int n) {
      System.out.println("\n*** ERROR: " + n);
      System.exit(1);
   }

   // treePrint: recursive inorder print of tree p 
   private void treePrint(tnode p) {
      if (p == null) System.out.print("0");
      else {
         // turn lowercase into uppercase 
         System.out.print("( " + Character.toUpperCase(p.ch) + " ");
         treePrint(p.left);
         System.out.print(" ");
         treePrint(p.right);
         System.out.print(" )");
      }
   }
          
   public static void main(String[] args) {
      TreeReadWrite tree = new TreeReadWrite();
      tree.bintree();
   }

}

// GetNext.java: fetch the next char or int from standard input
import java.io.*;
public class GetNext
{
   // in: reader for reading input data
   private static Reader in = new InputStreamReader(System.in); 

   // ch: holds the next character read
   private static char ch;

   public static char getNextChar() {
      try {
         ch = (char)in.read();
      }
      catch (Exception exception) 
      {
         System.out.println("Error reading character");
         ch = ' ';
      }
      return ch;
   }
}           

ten60% javac -deprecation TreeReadWrite.java
ten60% java TreeReadWrite
(a  0  0) #
( A 0 0 )#
ten60% java TreeReadWrite
(a  (b 0 0) (c 0 0) ) #
( A ( B 0 0 ) ( C 0 0 ) )#
ten60% java TreeReadWrite
(a (b (d 0 0) 0) (c (e 0 0) (f 0 0))) #
( A ( B ( D 0 0 ) 0 ) ( C ( E 0 0 ) ( F 0 0 ) ) )#
ten60% java TreeReadWrite
(m (f (a 0 (d 0 0)) (j 0 0)) (t (s (o (n 0 0) 0) 0) (w 0 0)))#
( M ( F ( A 0 ( D 0 0 ) ) ( J 0 0 ) ) ( T ( S ( O ( N 0 0 ) 0 ) 0 ) ( W 0 0 ) ) )#