Java正则表达式(1)

String类的三个内建正则表达式工具：

1.matches()方法

示例：检查一个句子是否以大写字母开头，以句号结尾　

     public static boolean checkFormat(String sentence){
         return sentence.matches("^[A-Z].+\\.$");
     }

2.split()方法

示例：以空格分割knights字符串并以数组形式返回

     public static void test(){
         String knights =
                 "Then, when you have found the shrubbery,"
                 + "you must cut down the mightiest tree in the forest... "
                 + "with... a herring";
         String newString = Arrays.toString(knights.split(" "));
         System.out.println(newString);
     }

3.replaceFirst()和replaceAll()方法

示例：替换knights字符串中所有元音字母为下划线

     public static void test(){
         String knights =
                 "Then, when you have found the shrubbery,"
                 + "you must cut down the mightiest tree in the forest... "
                 + "with... a herring";
         String newKnights = knights.replaceAll("[AaEeIiOoUu]", "_");
         System.out.println(newKnights);
     }

replaceFirst()方法只在首次出现时替换，replaceAll则替换所有满足条件的部分