JAVA正则表达式

package myPro;import java.util.regex.Matcher;import java.util.regex.Pattern;public class myPro {    public static void main(String args[]) {        /*        Pattern pattern = Pattern.compile("John");        Matcher matcher = pattern.matcher("John does this, and John does that");        String s2 = matcher.replaceAll("sam");        System.out.println("replaceAll = "+s2);        System.out.println("-----------------------------------------------");        StringBuffer s3 = new StringBuffer();        while(matcher.find()) {//每找到一次就输出一次            matcher.appendReplacement(s3, "sam");            System.out.println(s3.toString());        }        System.out.println("---------------------------------------------");        String s2 = matcher.replaceFirst("sam");        System.out.println("replaceFirst = "+s2);        System.out.println("-------------------------------------");        */        Pattern pattern = Pattern.compile("a");        Matcher matcher = pattern.matcher("This is a text");        while(matcher.find()) {            System.out.println("Match started at:"+matcher.start(0));            System.out.println("Match ended at :"+matcher.end(0));//输出最后一个元素的后一个位置        }    }}