正则表达式提取范围内的数字

Question

I want to extract numbers from 1 to 19 from the given string.

String n="1 21 16 17 9 8 22 20 10";
Pattern p=Pattern.compile("(1[0-9]|[0-9])");
Matcher m=p.matcher(n);
while(m.find())
    System.out.println(n.substring(m.start(),m.end()));
}

Output I obtain:

 1
 2
 1
 16
 17
 9
 8
 2
 2
 2
 0
10

Expected output should ignore 20 , 21 , 22 from the string. Right now, instead of that, 22 gets split into 2 and 2 in the display which is not expected.

Answer 1

Add word boundaries:

String n="1 21 16 17 9 8 22 20 10";
Pattern p=Pattern.compile("\\b(1[0-9]|[0-9])\\b");
Matcher m=p.matcher(n);
while(m.find())
    System.out.println(n.substring(m.start(),m.end()));
}

See demo

Answer 2

使用单词边界：

Pattern p=Pattern.compile("\\b(1[0-9]|[0-9])\\b");