用Java解释正则表达式“ \ A”元字符
子表达式/元字符“\A”匹配整个字符串的开头。
例子1
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class RegexExample {
public static void main( String args[] ) {
String regex = "\\AHi";
String input = "Hi how are you welcome to Nhooo";
Pattern p = Pattern.compile(regex);
Matcher m = p.matcher(input);
int count = 0;
while(m.find()) {
count++;
}
System.out.println("Number of matches: "+count);
}
}输出结果
Number of matches: 1
例2
以下Java程序接受来自用户的字符串，以验证它是否包含非ASCII字符。
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class StartingOfInput {
public static void main( String args[] ) {
String regex = "\\A\\p{ASCII}*\\z";
Scanner sc = new Scanner(System.in);
System.out.println("Enter the input string: ");
String input = sc.nextLine();
//创建一个Pattern对象
Pattern p = Pattern.compile(regex);
//创建一个Matcher对象
Matcher m = p.matcher(input);
if(m.find()) {
System.out.println("Given input contains only ASCII characters ");
} else {
System.out.println("Given input contains non-ASCII characters ");
}
}
}输出1
Enter the input string: What is your name Given input contains only ASCII characters
输出2
Enter the input string: whÿ do we fall Given input contains non-ASCII characters