Java中的 Matcher lookingAt() 方法及示例

Matcher 类的lookingAt()方法尝试在匹配器中部分或完全匹配模式。它返回一个布尔值，显示模式是否从模式的开头部分或完全匹配。

句法：

public boolean lookingAt()

参数：此方法不带任何参数。

返回值：此方法返回一个布尔值，显示输入序列的前缀是否匹配此匹配器的模式。

下面的示例说明了 Matcher.lookingAt() 方法：

示例 1：

// Java code to illustrate lookingAt() method
  
import java.util.regex.*;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // Get the regex to be checked
        String regex = "Geeks";
  
        // Create a pattern from regex
        Pattern pattern
            = Pattern.compile(regex);
  
        // Get the String to be matched
        String stringToBeMatched
            = "GeeksForGeeks";
  
        // Create a matcher for the input String
        Matcher matcher
            = pattern
                  .matcher(stringToBeMatched);
  
        // Get the possible result
        // using lookingAt() method
        System.out.println(matcher.lookingAt());
    }
}

输出：

true

示例 2：

// Java code to illustrate lookingAt() method
  
import java.util.regex.*;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // Get the regex to be checked
        String regex = "GFG";
  
        // Create a pattern from regex
        Pattern pattern
            = Pattern.compile(regex);
  
        // Get the String to be matched
        String stringToBeMatched
            = "GFGFGFGFGFGFGFGFGFG";
  
        // Create a matcher for the input String
        Matcher matcher
            = pattern
                  .matcher(stringToBeMatched);
  
        // Get the possible result
        // using lookingAt() method
        System.out.println(matcher.lookingAt());
    }
}

输出：

true

参考： https://docs.oracle.com/javase/9/docs/api/ Java/util/regex/Matcher.html#lookingAt–