java - 当我尝试打印所有组时，我得到 "IndexOutOfBoundsException: No group 4"

Question

我有代码为

 String regexpr = "(abc)(ab)(cd)";
 String test = "abcabcd";
 Pattern p = Pattern.compile(regexpr);
 Matcher m = p.matcher(test);
 while(m.find ())
 {
     System.out.println(m.group());
 }

此代码给出的输出为

abcabcd

But I want to print all the groups in the matched string i.e

group 1 abc
group 2 ab
group 3 cd

我试过了

int i=1;
while (m.group(i) != null)
{
    System.out.println("group" + i + m.group(i));
    i++;
}

我得到了

group 1 abc
group 2 ab
group 3 cd
Exception in thread "main" java.lang.IndexOutOfBoundsException: No group 4

如何避免这种异常？

以及如何打印所有组的开始和结束索引？

Answer 1

您可以打印所有组的开始和结束索引

   while (i<=m.groupCount())
       {
           System.out.println("group" + i + m.group(i));
           System.out.println("starting index:" + m.start(i) + "Ending Index:" + m.end(i));
           i++;
       }