format.java

Java2核心技术卷一 配套源码,看了还不错

      if (precision < 0) precision = 6;
      int s = 1;
      if (x < 0) { x = -x; s = -1; }
      if (fmt == 'f')
         r = fixed_format(x);
      else if (fmt == 'e' || fmt == 'E' || fmt == 'g' || fmt == 'G')
         r = exp_format(x);
      else throw new java.lang.IllegalArgumentException();
      
      return pad(sign(s, r));
   }

   /** 
      Formats an integer into a string (like sprintf in C)

      @param x the number to format
      @return the formatted string 
    */
   
   public String format(int x)
   {  long lx = x;
      if (fmt == 'o' || fmt == 'x' || fmt == 'X')
         lx &= 0xFFFFFFFFL; 
      return format(lx);
   }
   
   /** 
      Formats a long integer into a string (like sprintf in C)

      @param x the number to format
      @return the formatted string 
    */
   
   public String format(long x)
   {  String r; 
      int s = 0;
      if (fmt == 'd' || fmt == 'i')
      {  if (x < 0) 
         {  r = ("" + x).substring(1);
            s = -1; 
         }
         else 
         {  r = "" + x; 
            s = 1;
         }
      }
      else if (fmt == 'o')
         r = convert(x, 3, 7, "01234567");
      else if (fmt == 'x')
         r = convert(x, 4, 15, "0123456789abcdef");
      else if (fmt == 'X')
         r = convert(x, 4, 15, "0123456789ABCDEF");
      else throw new java.lang.IllegalArgumentException();
         
      return pad(sign(s, r));
   }
   
   /** 
      Formats a character into a string (like sprintf in C)

      @param x the value to format
      @return the formatted string 
    */
   
   public String format(char c)
   {  if (fmt != 'c')
         throw new java.lang.IllegalArgumentException();

      String r = "" + c;
      return pad(r);
   }
   
   /** 
      Formats a string into a larger string (like sprintf in C)

      @param x the value to format
      @return the formatted string 
    */
   
   public String format(String s)
   {  if (fmt != 's')
         throw new java.lang.IllegalArgumentException();
      if (precision >= 0 && precision < s.length())
         s = s.substring(0, precision);
      return pad(s);
   }
   
    
   /**
      a test stub for the format class
    */
   
   public static void main(String[] a)
   {  double x = 1.23456789012;
      double y = 123;
      double z = 1.2345e30;
      double w = 1.02;
      double u = 1.234e-5;
      int d = 0xCAFE;
      Format.printf("x = |%f|\n", x);
      Format.printf("u = |%20f|\n", u);
      Format.printf("x = |% .5f|\n", x);
      Format.printf("w = |%20.5f|\n", w);
      Format.printf("x = |%020.5f|\n", x);
      Format.printf("x = |%+20.5f|\n", x);
      Format.printf("x = |%+020.5f|\n", x);
      Format.printf("x = |% 020.5f|\n", x);
      Format.printf("y = |%#+20.5f|\n", y);
      Format.printf("y = |%-+20.5f|\n", y);
      Format.printf("z = |%20.5f|\n", z);
      
      Format.printf("x = |%e|\n", x);
      Format.printf("u = |%20e|\n", u);
      Format.printf("x = |% .5e|\n", x);
      Format.printf("w = |%20.5e|\n", w);
      Format.printf("x = |%020.5e|\n", x);
      Format.printf("x = |%+20.5e|\n", x);
      Format.printf("x = |%+020.5e|\n", x);
      Format.printf("x = |% 020.5e|\n", x);
      Format.printf("y = |%#+20.5e|\n", y);
      Format.printf("y = |%-+20.5e|\n", y);
      
      Format.printf("x = |%g|\n", x);
      Format.printf("z = |%g|\n", z);
      Format.printf("w = |%g|\n", w);
      Format.printf("u = |%g|\n", u);
      Format.printf("y = |%.2g|\n", y);
      Format.printf("y = |%#.2g|\n", y);

      Format.printf("d = |%d|\n", d);
      Format.printf("d = |%20d|\n", d);            
      Format.printf("d = |%020d|\n", d);    
      Format.printf("d = |%+20d|\n", d);
      Format.printf("d = |% 020d|\n", d);
      Format.printf("d = |%-20d|\n", d);
      Format.printf("d = |%20.8d|\n", d);
      Format.printf("d = |%x|\n", d);            
      Format.printf("d = |%20X|\n", d);    
      Format.printf("d = |%#20x|\n", d);
      Format.printf("d = |%020X|\n", d);
      Format.printf("d = |%20.8x|\n", d);
      Format.printf("d = |%o|\n", d);            
      Format.printf("d = |%020o|\n", d);    
      Format.printf("d = |%#20o|\n", d);
      Format.printf("d = |%#020o|\n", d);
      Format.printf("d = |%20.12o|\n", d);
      
      Format.printf("s = |%-20s|\n", "Hello");      
      Format.printf("s = |%-20c|\n", '!');      

      // regression test to confirm fix of reported bugs

      Format.printf("|%i|\n", Long.MIN_VALUE);

      Format.printf("|%6.2e|\n", 0.0);
      Format.printf("|%6.2g|\n", 0.0);

      Format.printf("|%6.2f|\n", 9.99);
      Format.printf("|%6.2f|\n", 9.999);

      Format.printf("|%6.0f|\n", 9.999);
      
      d = -1;
      Format.printf("d = |%X|\n", d);
   }
   
   private static String repeat(char c, int n)
   {  if (n <= 0) return "";
      StringBuffer s = new StringBuffer(n);
      for (int i = 0; i < n; i++) s.append(c);
      return s.toString();
   }

   private static String convert(long x, int n, int m, String d)
   {  if (x == 0) return "0";
      String r = "";
      while (x != 0)
      {  r = d.charAt((int)(x & m)) + r;
         x = x >>> n;
      }
      return r;
   }

   private String pad(String r)
   {  String p = repeat(' ', width - r.length());
      if (left_align) return pre + r + p + post;
      else return pre + p + r + post;
   }
   
   private String sign(int s, String r)
   {  String p = "";
      if (s < 0) p = "-"; 
      else if (s > 0)
      {  if (show_plus) p = "+";
         else if (show_space) p = " ";
      }
      else
      {  if (fmt == 'o' && alternate && r.length() > 0 && r.charAt(0) != '0') p = "0";
         else if (fmt == 'x' && alternate) p = "0x";
         else if (fmt == 'X' && alternate) p = "0X";
      }
      int w = 0;
      if (leading_zeroes) 
         w = width;
      else if ((fmt == 'd' || fmt == 'i' || fmt == 'x' || fmt == 'X' || fmt == 'o') 
         && precision > 0) w = precision;
      
      return p + repeat('0', w - p.length() - r.length()) + r;
   }
   
   private String fixed_format(double d)
   {  boolean removeTrailing
         = (fmt == 'G' || fmt == 'g') && !alternate;
         // remove trailing zeroes and decimal point

      if (d > 0x7FFFFFFFFFFFFFFFL) return exp_format(d);
      if (precision == 0) 
         return (long)(d + 0.5) + (removeTrailing ? "" : ".");

      long whole = (long)d;
      double fr = d - whole; // fractional part
      if (fr >= 1 || fr < 0) return exp_format(d);

      double factor = 1;
      String leading_zeroes = "";
      for (int i = 1; i <= precision && factor <= 0x7FFFFFFFFFFFFFFFL; i++) 
      {  factor *= 10; 
         leading_zeroes = leading_zeroes + "0"; 
      }
      long l = (long) (factor * fr + 0.5);
      if (l >= factor) { l = 0; whole++; } // CSH 10-25-97
      
      String z = leading_zeroes + l;
      z = "." + z.substring(z.length() - precision, z.length());

      if (removeTrailing)
      {  int t = z.length() - 1;
         while (t >= 0 && z.charAt(t) == '0') t--;
         if (t >= 0 && z.charAt(t) == '.') t--;
         z = z.substring(0, t + 1);
      }

      return whole + z;
   }

   private String exp_format(double d)
   {  String f = "";
      int e = 0;
      double dd = d;
      double factor = 1;
      if (d != 0)
      {  while (dd > 10) { e++; factor /= 10; dd = dd / 10; }
         while (dd < 1) { e--; factor *= 10; dd = dd * 10; }
      }
      if ((fmt == 'g' || fmt == 'G') && e >= -4 && e < precision) 
         return fixed_format(d);
      
      d = d * factor;
      f = f + fixed_format(d);
      
      if (fmt == 'e' || fmt == 'g')
         f = f + "e";
      else
         f = f + "E";

      String p = "000";      
      if (e >= 0) 
      {  f = f + "+";
         p = p + e;
      }
      else
      {  f = f + "-";
         p = p + (-e);
      }
         
      return f + p.substring(p.length() - 3, p.length());
   }
   
   private int width;
   private int precision;
   private String pre;
   private String post;
   private boolean leading_zeroes;
   private boolean show_plus;
   private boolean alternate;
   private boolean show_space;
   private boolean left_align;
   private char fmt; // one of cdeEfgGiosxXos
}