[正则表达式]通过几个简单的正则应用题来掌握正则的基本用方法和规则

1.验证手机号
匹配如下四个手机号
18079143050
15160819850
18765168050
14235412810

解析：
找规则:
1.以1开头 ==================== ^1
2.一共11位
3.50结尾===================== (50)$
4.倒数第三位是 0 或者 8========= [08]

合在一起为:1\d{7}[08](50)$

使用在线正则表达式工具检验一下：

编写代码：

public class Demo01 {
    public static void main(String[] args) {
     String telephoneNumber = "18079143050";
        String telephoneNumber2 = "15160819850";
        String telephoneNumber3 ="18765168050";
        String telephoneNumber4 ="14235412810";
        String regex = "^1\\d{7}[08](50)$";
        System.out.println(telephoneNumber.matches(regex));
        System.out.println(telephoneNumber2.matches(regex));
        System.out.println(telephoneNumber3.matches(regex));
        System.out.println(telephoneNumber4.matches(regex));
     }
}

运行结果

true
true
true
false
Process finished with exit code 0

2 . 将is替换替换成大写的IS
He is a man
This is a boy
is that your car?
isn’t it?
What is your name?

解析：
题干要求找出单独的 is 单词，而不是this, isn’t这样的单词

在线正则工具：

编写代码：

public class Demo01 {
    public static void main(String[] args) {
    String s = "He is a man\n" +
                "This is a boy\n" +
                "is that your car?\n" +
                "isn’t it?\n" +
                "What is your name?";
        String regex = "\\bis\\b";
        System.out.println(s.replaceAll(regex, "IS"));
   }
}

运行结果：

He IS a man
This IS a boy
IS that your car?
isn’t it?
What IS your name?

Process finished with exit code 0

3.日期替换
2016/03/05
1993/08/05
2016/11/24
12345/23/45678
12345/24/3356
1993-08-05
将正确的日期格式替换为03-05-2016
解析：
读题了解到需要查找的格式
1.先由4个数字组成年========== \d{4}
2.分割符号两种============== [-/]
3.两个数字组成的月份和日期==== \d{2}
4. 单词的分界处============== \b
组合成：\b(\d{4}[-/](\d{2})[-/](\d{2})\b

在线正则表达式工具：

编写代码：

public class Demo01 {
    public static void main(String[] args) {
     String r = "2016/03/05\n" +
                "1993/08/05\n" +
                "2016/11/24\n" +
                "12345/23/45678\n" +
                "12345/24/3356\n" +
                "1993-08-05";
        String regex = "\\b(\\d{4})[-/](\\d{2})[-/](\\d{2})\\b";
        System.out.println(r.replaceAll(regex, "$2-$3-$1"));
    }
}

运行结果：

03-05-2016
08-05-1993
11-24-2016
12345/23/45678
12345/24/3356
08-05-1993

Process finished with exit code 0

4. 获取以下英文句子中两个字符组成的单词并且输出

On Friendship And a youth said, “Speak to us of Friendship.”
Your friend is your needs answered. He is your field which

解析：
[A-Za-z]------表示所有的英文字母；
\b--------------单词的开头或结尾，也就是单词的分界处。
正则表达式为：
\b[A-Za-z][A-Za-z]\b

在线正则表达式工具检验：

编写代码：

public class Demo01 {
    public static void main(String[] args) {
     String W = "On Friendship And a youth said, " +
                "\"Speak to us of Friendship.\" " +
                "Your friend is your needs answered. He is your field which";
        String regex = "\\b[A-Za-z][A-Za-z]\\b";
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(W);
         while (matcher.find()) {
            System.out.print(" " + matcher.group());
        }
    }
}

运行结果：

 On to us of is He is
Process finished with exit code 0

5.将Hello402World13Java798Android56PHP 字符串中的数字提取出来并且转化成一个排好序的字符串输出。
例如 0123456789

解析：
这题只需要找出数字即可
\d-----------数字

编写代码

public class Demo01 {
    public static void main(String[] args) {
     String n = "Hello402World13Java798Android56PHP";
        String regex = "\\d+";
        Pattern p = Pattern.compile(regex);
        Matcher m = p.matcher(n);
        String result = "";
        while (m.find()){
           String group = m.group();
           result += group;
        }
       char[] chars = result.toCharArray();
        Arrays.sort(chars); //升序
        System.out.println(chars);
    }
}

运行结果：

0123456789

Process finished with exit code 0

总结：
这几道正则表达式的题比较基础，刚学习的同学可以试着做一下，可以很好的掌握和分析正则的使用方法和原则。