CIYAWASAY: 讀檔剖析文字新利器:Scanner

Friday, June 04, 2004

讀檔剖析文字新利器:Scanner

其實是從下面這篇文章看到的:
Programming with the New Language Features in J2SE 1.5
覺得實在是蠻好用的
所以跟大家簡單介紹一下~

java.util.Scanner是Java1.5新加入的文字處理類別
它可以把讀入的字串轉成各種 primitive type 像是 int, long....等
也可以用 regular expression 來剖析讀入的字串

API中有下列的範例:

從 console 讀入文字，並轉成 int (預設是以空白為分隔單位)

Scanner sc = new Scanner(System.in);
int i = sc.nextInt();

從檔案讀出 long

Scanner sc = new Scanner(new File("myNumbers"));
while (sc.hasNextLong()) {
   long aLong = sc.nextLong();
}

使用其他的分隔單位(delimiter)

String input = "1 fish 2 fish red fish blue fish";
Scanner s = new Scanner(input).useDelimiter("\\s*fish\\s*");
System.out.println(s.nextInt());
System.out.println(s.nextInt());
System.out.println(s.next());
System.out.println(s.next());
s.close();

1
2
red
blue

或是使用 regular expression 剖析

String input = "1 fish 2 fish red fish blue fish";
Scanner s = new Scanner(input);
s.findInLine("(\\d+) fish (\\d+) fish (\\w+) fish (\\w+)");
MatchResult result = s.match();
for (int i=1; i<=result.groupCount(); i++)
   System.out.println(result.group(i);
s.close();

其他我看到蠻有用的方法還有: