system.out.format("pi is approximately  %f", math.pi);

   system.out.printf("pi is approximately  %f", math.pi);

 printf()和 format() 方法具有相同的功能. system.out 是 java.io.printstream的实例. printstream, java.io.printwriter, 和 java.lang.string 每个类都有四个新的格式化方法:

format( string format, object... args);

printf( string format, object... args);

format( locale locale, string format, object... args);

printf( locale locale, string format, object... args);

formatter.format("pi is approximately %1$f," +

        "and e is about %2$f", math.pi, math.e);

%[argument_index$][flags][width][.precision]conversion

其中：

argument_index是一个正整数，说明了参数的位置，1为取第一个参数

width表示输出的最小字母个数

precision代表数字的小数位数

conversion代表被格式化的参数的类型：

f  float,

t  time

d  decimal

o octal

x  hexadecimal

s  general

c  a unicode character

package format;

   import java.util.formatter;

   public class usingformatter {

     public static void main(string[] args) {

       if (args.length != 1) {

         system.err.println("usage: " +

           "java format/usingformatter ");

         system.exit(0);

       }

       string format = args[0];

       stringbuilder stringbuilder = new stringbuilder();

       formatter formatter = new formatter(stringbuilder);

       formatter.format("pi is approximately " + format +

         ", and e is about " + format, math.pi, math.e);

       system.out.println(stringbuilder);

     }

   }

//控制台调用

java format/usingformatter %f

//输出

pi is approximately 3.141593, and e is about 2.718282

//控制台调用

java format/usingformatter %.2f

//输出

pi is approximately 3.14, and e is about 2.72

//控制台调用

java format/usingformatter %6.2f

//输出(有空格来填补长度)

pi is approximately   3.14, and e is about   2.72

//控制台调用

java format/usingformatter  %1$.2f

//输出

pi is approximately 3.14, and e is about 3.14

//改变区域设置

package format;

   import java.util.formatter;

   import java.util.locale;

   public class usingformatter {

     public static void main(string[] args) {

       if (args.length != 1) {

         system.err.println("usage: " +

           "java format/usingformatter <format string>");

         system.exit(0);

       }

       string format = args[0];

       stringbuilder stringbuilder = new stringbuilder();

       formatter formatter = new formatter(stringbuilder,

                                   locale.france);

       formatter.format("pi is approximately " + format +

         ", and e is about " + format, math.pi, math.e);

       system.out.println(stringbuilder);

     }

   }

//控制台调用

java format/usingformatter %.2f

//输出

pi is approximately 3,14, and e is about 2,72

//采用format,printf的可替代写法

package format;

   public class usingsystemout {

     public static void main(string[] args) {

       if (args.length != 1) {

         system.err.println("usage: " +

           "java format/usingsystemout <format string>");

         system.exit(0);

       }

       string format = args[0];

       system.out.format("pi is approximately " + format +

         ", and e is approximately " + format, math.pi, math.e);

     }

   }

//控制台调用

java format/usingsystemout %.2f%n

//输出

pi is approximately 3.14

   , and e is about 2.72

tr  hour and minute,

ta  the day of the week

tb  the name of the month

te  the number of the day of the month

ty  the year

//eg.

package format;

   import java.util.calendar;

   public class formattingdates  {

     public static void main(string[] args) {

       system.out.printf("right now it is %tr on " +

                         "%<ta, %<tb %<te, %<ty.%n",

                         calendar.getinstance());

     }

   }

//说明：“<”指示采用的参数为前一个被格式化的参数

//输出

right now it is 01:55:19 pm on wednesday, september 22, 2004.