字符串处理利器-正则表达式

正则表达式

一、常见的符号的介绍

　　1.1 预定义字符类

　　1.2 数量词

　　1.3 边界匹配符号

　　　1.3 其他常见符号

二.正则表达式的示例

public class Test {
    public static void main(String[] args){
        //简单认知正则表达式的概念
        p("abc".matches("..."));
        p("a8729a".replaceAll("\\d", "-"));

        Pattern p = Pattern.compile("[a-z]{3}");
        Matcher m = p.matcher("fgh");

        p(m.matches());

        p("fgha".matches("[a-z]{3}"));

        //初步认识 . * + ?
        p("----------------初步认识-----------------");
        p("a".matches("."));//true
        p("aa".matches("aa"));//true
        p("aaaa".matches("a*"));//true
        p("aaaa".matches("a+"));//true
        p("".matches("a*"));//true
        p("aaaa".matches("a?"));//false
        p("".matches("a?"));//true
        p("213442142342".matches("\\d{3,100}"));//true
        p("192.168.0.aaa".matches("\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}"));//false
        p("192".matches("[0-2][0-9][0-9]"));

        //范围
        p("-------------范围------------");
        p("a".matches("[abc]"));//true
        p("a".matches("[^abc]"));//false
        p("A".matches("[a-zA-Z]"));//true
        p("A".matches("[a-z]|[A-Z]"));//true
        p("A".matches("[a-z[A-Z]]"));//true
        p("R".matches("[A-Z&&[RFG]]"));//true

        //认识 \s \w \d
        /**在正则表达式里两个\\会被当成一个反斜杠  **/
        p("认识 \\s\\w\\d");
        p(" \n\r\t".matches("\\s{4}"));
        p(" ".matches("/S"));
        p("a_8".matches("\\w{3}"));
        p("abc888&^%".matches("[a-z]{1,3}\\d+[&^#%]+"));
        p("\\".matches("\\\\"));

        //boundary
        p("-----------------boundary-----------------");
        p("hello sir".matches("^h.*"));
        p("hello sir".matches(".*ir$"));
        p("hello sir".matches("^h[a-z]{1,3}o\\b.*"));
        p("hellosir".matches("^h[a-z]{1,3}o\\b.*"));
        //white line
        p(" \n".matches("^[\\s&&[^\n]]*\\n$"));

        //email
        p("----------------email--------------");
        p("[email protected]".matches("[\\w[.-]][email protected][\\w[.-]]+\\.\\w+"));

        //matches find lookingAt
        p("------matches find lookingAt");
        Pattern p1 = Pattern.compile("\\d{3,5}");
        String s = "123-2345-234-00";
        Matcher m1 = p1.matcher(s);
        p(m1.matches());
        m1.reset();
        p(m1.find());
        //找的到 才会返回 start 起始位置 和 终止位置 找不到则报错
        p(m1.start() + "-" + m1.end());
        p(m1.find());
        p(m1.start() + "-" + m1.end());
        p(m1.find());
        p(m1.start() + "-" + m1.end());
        p(m1.find());

        p(m1.lookingAt());

        //replacement
        p("----------------replacement----------------");
        Pattern p3 = Pattern.compile("java",Pattern.CASE_INSENSITIVE);
        Matcher matcher3 = p3.matcher("java JaVa ashfaks JAVA iloveJAva youhatejAVA DAFAD");
        //p(matcher3.replaceAll("JAVA"));
        StringBuffer buf = new StringBuffer();
        int i = 1;
        while(matcher3.find()){
            if(i % 2 == 0){
                matcher3.appendReplacement(buf, "java");
            }else{
                matcher3.appendReplacement(buf, "JAVA");
            }
            i++;
        }
        matcher3.appendTail(buf);
        p(buf);

        //group
        p("--------------group------------");
        Pattern gp = Pattern.compile("(\\d{3,5})([a-z]{2})");
        String str = "123aa-34345bb-234cc-00";
        Matcher gm = gp.matcher(str);
        while(gm.find()){
            p(gm.group());
        }
    }

    public static void p(Object o){
        System.out.println(o);
    }

}

原文地址：https://www.cnblogs.com/dwlovelife/p/9919392.html