查找字符串中最后一个非数字字符的索引

Question

String foo = "987abc<*(123";

我对RegEx-es和类似的搜索模式非常缺乏经验，而且我所尝试的每一种方法都不能正常工作（大多数情况下会导致StringIndexOutOfBoundsException)。

找到字符串中最后一组数字开始的索引的可靠而简单的方法是什么？

Answer 1

注意：“1”在字符串的索引8处。

如果您不想要它，就没有必要为此使用RegEx。

像这样的方法应该完成以下工作：

public static int findLastNumbersIndex(String s) {
  boolean numberFound = false;
  boolean charBeforeNumberFound = false;

  //start at the end of the String
  int index = s.length() - 1;

  //loop from the back to the front while there are more chars 
  //and no nonDigit is found before a digit
  while (index >= 0 && !charBeforeNumberFound) {
    //when the first number was found, set the boolean flag
    if (!numberFound && Character.isDigit(s.charAt(index))) {
      numberFound = true;
    }

    //when already a number was found and there is any nonDigit stop the execution
    if (numberFound && !Character.isDigit(s.charAt(index))) {
      charBeforeNumberFound = true;
      break;
    }

    index--;
  }
   
  return index + 1;
}

public static void main(String[] args) {
  System.out.println("\"987abc<*123\"" + " index of lastNumberSet: " + findLastNumbersIndex("987abc<*123"));
  System.out.println("\"987abc<*123abc\"" + " index of lastNumberSet: " + findLastNumbersIndex("987abc<*123abc"));
  System.out.println("\"987abc\"" + " index of lastNumberSet: " + findLastNumbersIndex("987abc"));
  System.out.println("\"abc987\"" + " index of lastNumberSet: " + findLastNumbersIndex("abc987"));
  System.out.println("\"987\"" + " index of lastNumberSet: " + findLastNumbersIndex("987"));
  System.out.println("(Empty String)" + " index of lastNumberSet: " + findLastNumbersIndex(""));
  System.out.println("\"abc\"" + " index of lastNumberSet: " + findLastNumbersIndex("abc"));
}

"987abc<*123" index of lastNumberSet: 8
"987abc<*123abc" index of lastNumberSet: 8
"987abc" index of lastNumberSet: 0
"abc987" index of lastNumberSet: 3
"987" index of lastNumberSet: 0
(Empty String) index of lastNumberSet: 0
"abc" index of lastNumberSet: 0