Java.util.formmatter

创建于：2014-04-18 | 分类： java初级码农  | 标签： Java  基础 

public final class Formatter extends Object implements Closeable, Flushable

printf风格的格式字符串的解释程序。此类提供了对布局对齐和排列的支持，以及对数值、字符串和日期/时间数据的常规格式和特定于语言环境的输出的支持。支持诸如 byte、BigDecimal 和 Calendar 等常见 Java 类型。任意用户类型的受限格式化定制都是通过 Formattable 接口提供的。

Formatter 对于多线程访问而言没必要是安全的。线程安全是可选的，它对此类中的方法用户负责。

示例程序(JUnit演示)

import java.util.Calendar;
import java.util.Formatter;
import java.util.GregorianCalendar;
import java.util.Locale;
import org.junit.Before;
import org.junit.Test;
import static java.util.Calendar.*;
import static org.junit.Assert.*;

public class FormatterTest {

private Formatter formatter;

@Before
public void setUp(){
    StringBuilder sb = new StringBuilder();
    formatter = new Formatter(sb,Locale.US);         
}

//字符串填充、注意顺序
@Test
public void demoTest(){ 
     formatter = formatter.format("%4$2s %3$2s %2$2s %1$2s",
             "a", "b", "c", "d");
     assertEquals(" d  c  b  a", formatter.toString());     
}

//数字填充，注意空格，加号，逗号
@Test
public void demoTest1(){
     formatter = formatter.format(Locale.FRANCE, "e = %+10.4f", Math.E);
     assertEquals("e =    +2,7183", formatter.toString()); 
}

//浮点型数字填充，注意负号处理，逗号，小数点，括号
@Test
public void demoTest2(){    
     formatter =   formatter.format("Amount gained or lost since last statement: $ %(,.2f",
             -6217.58F);
     assertEquals("Amount gained or lost since last statement: $ (6,217.58)", 
             formatter.toString()); 
}

//系统格式化输出
@Test
public void demoTest3System(){
       // Writes a formatted string to System.out.
       System.out.format("Local time: %tT", Calendar.getInstance());
       // -> "Local time: 13:34:18"

       // Writes formatted output to System.err.
       System.err.printf("Unable to open file '%1$s': %2$s",
                         "food", "No such file or directory");
       // -> "Unable to open file 'food': No such file or directory"

}

//处理日期
@Test
public void demoTest4String(){
      Calendar c = new GregorianCalendar(1995, MAY, 23);
      String s = String.format("Duke's Birthday: %1$tm %1$te, %1$tY", c);
      assertEquals("Duke's Birthday: 05 23, 1995", s); 
}       
}

说明

使用时，可查阅JAVA API