Need a way to get to get the pattern in a string matched with List.stream().anyMatch()

user_8547143 0
Viewed 92

I'm matching a list of strings against a list of keywords. The goal is to get a string only one time if it has any of the keywords in it.

Actually I'm doing it with this loop:

for (int i = 0; i < keywords.size(); i++) {
   if (text.toLowerCase().contains(keywords.get(i))) {
      System.out.println("keyword >>> " + keywords.get(i)
         + " text >>> " + text);
      break;
   }
}

I like to know if there is a way to get the keyword if I'm using the java stream API like so:

if (keywords.stream().anyMatch(text.toLowerCase()::contains)) {
   System.out.println("keyword >>> " + "how to get the keyword here"
         + " text >>> " + text);
}
java-stream java
3 Answers

anyMatch returns a boolean

Using .filter() & findFirst() you can retrieve a value. Note that if you use findFirst() you get an Optional<String> and could either use ifPresent() like this:

keywords.stream()
    .filter(keyword -> text.toLowerCase().contains(keyword))
    .findFirst()
    .ifPresent(keyWord -> System.out.println("[2] keyword >>> " + keyWord + " text >>> " + text));

Or with Optional.isPresent() & Optional.get():

Optional<String> firstKey = keywords.stream()
    .filter(keyword -> text.toLowerCase().contains(keyword))
    .findFirst();

if (firstKey.isPresent()) {
    System.out.println("[2] keyword >>> " + firstKey.get() + " | text >>> " + text);
}
user_67953240

As a less fancy alternative to stream there is a nicer for syntax in Java 1.6+

for(String keyword: keywords) {
    if (text.toLowerCase().contains(keyword)) {
        System.out.println("keyword >>> " + keyword
                + "text >>> " + text);
        break;
    }
}

I find the for syntax easier to read than the stream syntax. In a previous job I did a lot of C++ lambda functions with BOOST and the code was hard to parse, and the errors hard to trace.

user_3694460

Another option would be to print an informational message if the keyword was not found. This is easily done by moving the isPresent test inside the print statement.

List<String> keywords =
        Arrays.asList("now", "is", "the", "time");
String text = "what are your names?";
        
Optional<String> opt = keywords.stream()
            .filter(keyword -> text
                    .toLowerCase().contains(keyword))
            .findFirst();


System.out.println(!opt.isPresent() ? "No keyword was found!" : 
                                "keyword >>> " + opt.get() 
                                        + " text >>> " + text);

Prints

No keyword was found!
user_15525340
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