Java Scanner

一、扫描控制台输入

 

这个例子是常常会用到，但是如果没有Scanner，你写写就知道多难受了。

当通过new Scanner(System.in)创建一个Scanner，控制台会一直等待输入，直到敲回车键结束，把所输入的内容传给Scanner，作为扫描对象。如果要获取输入的内容，则只需要调用Scanner的nextLine()方法即可。

 

/**
* 扫描控制台输入
*
* @author leizhimin 2009-7-24 11:24:47
*/
public class TestScanner {
         public static void main(String[] args) {
                Scanner s = new Scanner(System.in);
                System.out.println( "请输入字符串：");
                 while ( true) {
                        String line = s.nextLine();
                         if (line.equals( "exit")) break;
                        System.out.println( ">>>" + line);
                }
        }
}

 

请输入字符串：
234
>>>234
wer
>>>wer
bye
>>>bye
exit

Process finished with exit code 0

 

先写这里吧，有空再继续完善。

 

二、如果说Scanner使用简便，不如说Scanner的构造器支持多种方式，构建Scanner的对象很方便。

 

可以从字符串（ Readable）、输入流、文件等等来直接构建Scanner对象，有了Scanner了，就可以逐段（根据正则分隔式）来扫描整个文本，并对扫描后的结果做想要的处理。

 

三、Scanner默认使用空格作为分割符来分隔文本，但允许你指定新的分隔符

 

使用默认的空格分隔符：

         public static void main(String[] args) throws FileNotFoundException {
                Scanner s = new Scanner( "123 asdf sd 45 789 sdf asdfl,sdf.sdfl,asdf    ......asdfkl    las");
//                s.useDelimiter(" |,|\\.");
                 while (s.hasNext()) {
                        System.out.println(s.next());
                }
        }

 

123
asdf
sd
45
789
sdf
asdfl,sdf.sdfl,asdf
......asdfkl
las

Process finished with exit code 0

 

将注释行去掉，使用空格或逗号或点号作为分隔符，输出结果如下：

123
asdf
sd
45
789
sdf
asdfl
sdf
sdfl
asdf







asdfkl

las

Process finished with exit code 0

 

 

Scanning with regular expressions
In addition to scanning for predefined primitive types, you can also scan for your own user-defined patterns, which is helpful when scanning more complex data. This example scans threat data from a log like your firewall might produce:
//: strings/ThreatAnalyzer.java
import java.util.regex.*;
import java.util.*;
public class ThreatAnalyzer {
static String threatData =
"58.27.82.161@02/10/2005\n" +
"204.45.234.40@02/11/2005\n" +
"58.27.82.161@02/11/2005\n" +
"58.27.82.161@02/12/2005\n" +
"58.27.82.161@02/12/2005\n" +
"[Next log section with different data format]";
public static void main(String[] args) {
Scanner scanner = new Scanner(threatData);
String pattern = "(\\d+[.]\\d+[.]\\d+[.]\\d+)@" +
"(\\d{2}/\\d{2}/\\d{4})";
while(scanner.hasNext(pattern)) {
scanner.next(pattern);
MatchResult match = scanner.match();
String ip = match.group(1);
String date = match.group(2);
System.out.format("Threat on %s from %s\n", date,ip);
}
}
} /* Output:
Threat on 02/10/2005 from 58.27.82.161
Threat on 02/11/2005 from 204.45.234.40
Threat on 02/11/2005 from 58.27.82.161
Threat on 02/12/2005 from 58.27.82.161
Threat on 02/12/2005 from 58.27.82.161

*///:~