Java8: Looking for a better way of parsing a text of "key: value" lines

I have a String of text lines.
Some of the lines have a format of "key: value". Others should be ignored.
I have a fixed (pre-defined) list of keys that I needs to extract values for and put into a HashMap.
So, I'm doing something like this:

BufferedReader reader = new BufferedReader(new StringReader(memoText));

reader.lines().forEach(line->{
    if(line.startsWith("prefix1")){
        // Some code is required here to get the value1
    }  
    else if(line.startsWith("prefix2")){
        // Some code is required here to get the value2
    }  
    ...
}

Is there a better way of implementing the parsing in Java 8?