如何获取字符串中第一个和最后一个字符的索引？

Question

Assume the below string :

String value = "161207CAD140000,0";

how can i get the index of the first char and the index of the last char for the substring CAD notice that the size of the substring may be changed from 2 ,3 or etc chars i want the solution to be dynamic.

Answer 1

You can use String.indexOf(String str) function which will return starting indexof the "CAD". Then add one less then the length of String to find in the returned value, that will be your last character index of "CAD".

Something like this:

String value = "161207CAD140000,0";
String str = "CAD";
String datePart = value.substring(0, value.indexOf(str)); // for finding the date part
String amountStr = value.substring(value.indexOf(str) + str.length()); //for finding the amount part
System.out.println(datePart +"  "+amountStr);`

Now suppose the String "CAD" is dynamic and you don't know what value it will have, in that case its better to use regex. Please see below code snippet:

String value = "161207CAD140000,0";
String patt = "[\\d,]+";
Pattern pattern = Pattern.compile(patt);
Matcher matcher = pattern.matcher(value);

while(matcher.find()){

    System.out.println(matcher.group());
}

If any question let me know in comments. Hope it helps.

Answer 2

This would do the job for any string.

String value = "161207CAD140000,0";
String searchedString = "CAD"
int firstIndex = value.indexOf(searchedString);
int lastCharIndex = firstIndex + searchedString.length();

Answer 3

There are methods in the String class for such requirements. You can use the indexOf and lastIndexOf methods to get the positions. eg

int index = value.indexOf("C"); //This returns 6
int lastIndex = value.lastIndexOf("D"); //this returns 8