[FIXED] Explanation of how the code behind indexing multiple occurrences of character in a string works

Issue

The program itself is supposed to take a string and find all the indexes of it inside another string.
Just as an example scanner stores data from the user, so in this case I've just written it without the use of a scanner:

String input = "asdesdu";
String largestStr = "sd";

String tempInput = input;        
while (tempInput.indexOf(largestStr) != -1) {
    int index = tempInput.indexOf(largestStr);            
    tempInput = tempInput.substring(index + 1);
}

So, from what I can gather the string tempInput is made with the same value as input in order for the while loop to stop running after it is run once because the value changes, however my question is why does tempInput also need to be used to find the index rather than using the original input string as shown below:

String tempInput = input;        
while (tempInput.indexOf(largestStr) != -1) {
    int index = input.indexOf(largestStr);            
    tempInput = tempInput.substring(index + 1);
}

I'm relatively new to java so any help or feedback is greatly appreciated.

Solution

As I understand the code, it searches for all occurences of largestStr in input.

int index = input.indexOf(largestStr); won't work here because it would always search for the occurence of largestStr from the beginning of input. So you will basically always get the same index.

What would work were saving the last index and searching from that index. Something like:

for (int index = input.indexOf(largestStr); index != -1; index = input.indexOf(largestStr, index + 1)) {
    // Do whatever you want with index
}

Answered By - lexicore