Java Scanner

http://blog.csdn.net/carolzhang8406/article/details/6726589

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

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());

}

asdf

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:

asdf

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” +

“[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

*///:~

Contents

Java Scanner