分类:
2008-10-17 13:28:48
DK5.0允许象C语言那样直接用printf()方法来格式化输出,并且提供了许多参数来格式化输入,调用也很简单:
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);
同时,以前的formatter类也提供了更完善的方法来格式化,例如:
formatter.format("Pi is approximately %1$f," +
"and e is about %2$f", Math.PI, Math.E);
格式化元素的构成如下:
%[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
以下是个例子:
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);
}
}
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