一、匹配

public class RegularExpressionDemo{
    public static void main(String[] args){
        
        //匹配电话号码
        String telphoneNum= "0015012828944";
        String reg= "^(13[0-9]|14[579]|15[0-3,5-9]|16[6]|17[0135678]|18[0-9]|19[89])\\d{8}$";
        System.out.println(telphoneNum.matches(reg));
        
    }
}

二、切割

public class RegularExpressionDemo{
    public static void main(String[] args){
        
        //把语句切割为单词
        String sentence = "welcome  to  china ";
        String reg = " +";
        String[] words = sentence.split(reg);
        for(String word : words){
            System.out.println(word);
        }
    }
}

三、替换

public class RegularExpressionDemo{
    public static void main(String[] args){
        
        //把字符串中的标点符号换成空
        String sentence = "How are you? Fine, thanks.";
        String reg = "[?,.]";
        sentence = sentence.replaceAll(reg,"");
        System.out.println(sentence);
    }
}

四、获取

import java.util.regex.Pattern;
import java.util.regex.Matcher;

public class RegularExpressionDemo{
    public static void main(String[] args){
        
        //获取句子中所有长度为3的单词
        String sentence = "How old are you? I'm 27 years old. what about you? So am I.";
        String reg = "[a-zA-Z]{3}";
        
        Pattern p = Pattern.compile(reg);
        Matcher m = p.matcher(sentence);
        
        while(m.find()){
            System.out.println(m.group());
        }
    }
}