Print Indentifier

import java.io.*;

public class Main {
  private final PushbackReader in;
  private final StringBuilder sb;

  public Main(PushbackReader in) {
    this.in = in;
    sb = new StringBuilder();
  }

  private char read() {
    int read_in = 0;
    try {
      read_in = in.read();
    }
    catch (Exception e) {
      System.exit(1);
    }
    if (read_in == -1) return Character.MIN_VALUE;
    return (char )read_in;
  }

  private void pushBack(char c) {
    try {
      in.unread(c);
    }
    catch (Exception e) {
      System.exit(1);
    }
  }

  public void parse() {
    while (true) {
      char c = read();
      if (c == Character.MIN_VALUE) break;
      if (isLineComment(c)) {
        lineComment();
        continue;
      }
      if (isBlockComment(c)) {
        blockComment();
        continue;
      }
      if (isBreakable(c)) {
        sb.append("\n");
        continue;
      }
      sb.append(c);
    }
  }

  private boolean isBlockComment(char c1) {
    return isComment(c1, '*');
  }

  private boolean isLineComment(char c1) {
    return isComment(c1, '/');
  }

  private boolean isComment(char c1, char comment_char) {
    if (c1 != '/') return false;
    char c2 = read();
    if (c2 != comment_char) {
      pushBack(c2);
      return false;
    }
    sb.append(c1); // c1 is /
    sb.append(c2); // c2 is / or *
    return true;
  }

  private boolean isBreakable(char c) {
    if (Character.isUnicodeIdentifierStart(c) ||
      Character.isUnicodeIdentifierPart(c)) return false;
    return true;
  }

  private void blockComment() {
    char prev = Character.MAX_VALUE;
    do {
      char c1 = read();
      if (c1 == Character.MIN_VALUE) break;
      sb.append(c1);
      if (prev == '*' && c1 == '/') break;
      char c2 = read();
      if (c2 == Character.MIN_VALUE) break;
      sb.append(c2);
      if (c1 == '*' && c2 == '/') break;
      prev = c2;
    } while (true);
    sb.append("\n");
  }

  private void lineComment() {
    while (true) {
      char c = read();
      if (c == Character.MIN_VALUE || c == Character.LINE_SEPARATOR ||
        c == '\r' || c == '\n') break;
      sb.append(c);
    }
    sb.append("\n");
  }

  @Override
  public String toString() {
    return sb.toString();
  }

  public static void main(String[] args) {
    PushbackReader in = null;
    if (args.length > 0) {
      File file = null;
      try {
        file = new File(args[0]);
      }
      catch (Exception e) {
        System.exit(1);
      }
      try {
        in = new PushbackReader(new FileReader(file));
      }
      catch (Exception e) {
        System.exit(1);
      }
    }
    else in = new PushbackReader(new InputStreamReader(System.in));
    Main m = new Main(in);
    m.parse();
    System.out.println(m);
  }
}