How to achieve the output using java lambda function rather than iterating through for loop in?

dkc 0
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Here is my code. I'd like to achieve the output without using for loop. Tried different ways in Java with help of lambda expression but it didn't work. Any help/suggestions would be very helpful. Thank you!


public class Hobbies {
    
    private final HashMap<String, String[]> hobbies = new HashMap<String, String[]>();
    
    public void add(String hobbyist, String... hobbies) {
        this.hobbies.put(hobbyist, hobbies);
    }
    
    public List<String> findAllHobbyists(String hobby) {
        
        List<String> hobbyyist = new ArrayList<String>();
         
        for (Entry<String, String[]> entry : hobbies.entrySet()) {
            String name = entry.getKey();
            String[] list = entry.getValue();
            
            for(String s: list) {
                if(s.equalsIgnoreCase(hobby))
                    hobbyyist.add(name);
            }
        }  
        
        
        return hobbyyist;
    }
    
    public static void main(String[] args) {
        Hobbies hobbies = new Hobbies();
        hobbies.add("Steve", "Fashion", "Piano", "Reading");
        hobbies.add("Patty", "Drama", "Magic", "Pets");
        hobbies.add("Chad", "Puzzles", "Pets", "Yoga");

        System.out.println(Arrays.toString(hobbies.findAllHobbyists("Yoga").toArray()));
        
        
    }
}
lambda java
1 Answers

Try this:

public List<String> findAllHobbyists(String hobby) {
        return hobbies.entrySet().stream()
                .filter(nameToHobbies -> Arrays.stream(nameToHobbies.getValue()).anyMatch(aHobby -> aHobby.equalsIgnoreCase(hobby)))
                .map(Map.Entry::getKey)
                .collect(Collectors.toList());
}

Also I'll suggest to rename hobbies map to namesToHobbies.

Also you can omit converting a list to an array in main:

public String[] findAllHobbyists(String hobby) {
        return hobbies.entrySet().stream()
                .filter(nameToHobbies -> Arrays.stream(nameToHobbies.getValue()).anyMatch(aHobby -> aHobby.equalsIgnoreCase(hobby)))
                .map(Map.Entry::getKey)
                .toArray(String[]::new)
}
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