正则表达式在Java中应用的三种典型场合：验证，查找和替换

正则式在编程中常用，总结在此以备考：

package regularexp;

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

public class RegUsages {
    // 验证例子
    private static boolean verify(String code) {
        final String patternStr = "\d+";
        return Pattern.matches(patternStr, code);
    }
    // 查找例子
    private static void search() {
        Pattern pattern = Pattern.compile("m(o+)n", Pattern.CASE_INSENSITIVE);
        
        Matcher matcher=pattern.matcher("Sun Earth moon mooon Mon mooooon Mooon Mars");
        while(matcher.find()) {
            System.out.println(String.format("%s (%d~%d)", matcher.group(0),matcher.start(),matcher.end()));
        }
    }
    // 更替例子1
    private static void replace1() {
        String str = "10元 1000人民币 10000元 100000RMB";
        str = str.replaceAll("(\d+)(元|人民币|RMB)", "$1圆");
        System.out.println(str);
    }
    // 更替例子2
    private static void replace2() {
        Pattern p = Pattern.compile("m(o+)n", Pattern.CASE_INSENSITIVE);

        Matcher m = p.matcher("Sun Earth moon mooon Mon mooooon Mooon Mars");
        StringBuffer sb = new StringBuffer();

        boolean result = m.find();

        while (result) {
            m.appendReplacement(sb, "Moon");
            result = m.find();
        }
        m.appendTail(sb);

        System.out.println("Result=" + sb.toString());
    }
    
    public static void main(String[] args) {
        System.out.println(String.format("601857 %s a stock code.",verify("601857")?"is":"isn't"));
        search();
        replace1();
        replace2();
    }
}

输出：

601857 is a stock code.
moon (10~14)
mooon (15~20)
Mon (21~24)
mooooon (25~32)
Mooon (33~38)
10圆 1000圆 10000圆 100000圆
Result=Sun Earth Moon Moon Moon Moon Moon Mars

--2020-03-06--