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