Java：获取字符串中匹配项位置的方法？

Question

String match = "hello";

String text = "0123456789hello0123456789";

int position = getPosition(match, text); // should be 10, is there such a method?

Answer 1

执行此操作的方法家族是：int indexOf(String str)indexOf(String str, int fromIndex)int lastIndexOf(String str)lastIndexOf(String str, int fromIndex)返回指定子字符串的第一个（或最后一个）出现在此字符串内的索引[ 从指定索引处开始向前（或向后搜索）]。String text = "0123hello9012hello8901hello7890";String word = "hello";System.out.println(text.indexOf(word)); // prints "4"System.out.println(text.lastIndexOf(word)); // prints "22"// find all occurrences forwardfor (int i = -1; (i = text.indexOf(word, i + 1)) != -1; i++) {    System.out.println(i);} // prints "4", "13", "22"// find all occurrences backwardfor (int i = text.length(); (i = text.lastIndexOf(word, i - 1)) != -1; i++) {    System.out.println(i);} // prints "22", "13", "4"

Answer 2

这使用正则表达式工作。String text = "I love you so much";String wordToFind = "love";Pattern word = Pattern.compile(wordToFind);Matcher match = word.matcher(text);while (match.find()) {     System.out.println("Found love at index "+ match.start() +" - "+ (match.end()-1));}输出：在索引2-5中找到“爱”一般规则 ：正则表达式从左到右搜索，并且一旦使用了匹配字符，便无法重复使用。

Answer 3

查找单个索引正如其他人所说，用于text.indexOf(match)查找单个匹配项。String text = "0123456789hello0123456789";String match = "hello";int position = text.indexOf(match); // position = 10查找多个索引由于@StephenC对代码可维护性的评论以及我自己在理解@polygenelubricants的答案方面的困难，我想找到另一种方法来获取文本字符串中匹配项的所有索引。以下代码（通过此答案进行了修改）做到了：String text = "0123hello9012hello8901hello7890";String match = "hello";int index = text.indexOf(match);int matchLength = match.length();while (index >= 0) {  // indexOf returns -1 if no match found    System.out.println(index);    index = text.indexOf(match, index + matchLength);}