Java indexOf method for multiple matches in String

Question

I had a question about the indexOf method. I want to find multiple cases of \"X\" in a string.

Suppose my string is \"x is x is x is x\", I want to find x in all of

Answer 1

Here is the solution with Streams API :

String text = "Lets search for E ?";

final char key = "e".charAt(0);
int[] indices = IntStream.range(0, text.length())
    .filter(i -> text.charAt(i) == key)
    .toArray();

Output will be like this :

//1
//6

If you want to add upper case letters into your result, you need to change the filter's argument closure with :

.filter(i -> Character.toLowerCase(text.charAt(i)) == key)

Then the output will be like this :

//1
//6
//16

Additionally if you just want to use the results or print it out for quick testing purposes you can do it with using forEach terminal operation:

IntStream.range(0, text.length())
    .filter(i -> text.charAt(i) == key)
    .forEach(System.out::println);