آموزش Map در جاوا: استفاده از HashMap, LinkedHashMap و TreeMap

Map<String, Integer> map = new HashMap<>();

map.put("Rick", 52);
map.put("Carl", 32);
map.put("Rosita", 38);
map.put("Henry", 32);
map.put("Maggie", 33);
map.put("Negan", 45);

System.out.println("Display entries in map: ");
System.out.println(map + "\n");

System.out.println("Is Bijan in list?" + map.containsKey("Bijan"));
System.out.println("Do we have 32 yo person? " + map.containsValue(32));
System.out.println("List of names in map: ");
System.out.println(map.keySet());
System.out.println("List of Ages in map: ");
System.out.println(map.values() + "\n");
        

LinkedHashMap<String, Integer> linkedHashMap = new LinkedHashMap<>();

linkedHashMap.put("Rick", 52);
linkedHashMap.put("Carl", 32);
linkedHashMap.put("Rosita", 38);
linkedHashMap.put("Henry", 32);
linkedHashMap.put("Maggie", 33);
linkedHashMap.put("Negan", 45);

linkedHashMap.forEach((name, age) -> System.out.println("name: " + name + " age: " + age));
System.out.println();

System.out.println("Updating map by changing Maggie's age and re ordering it as first entry: ");
int oldAge = linkedHashMap.putFirst("Maggie", 27);
System.out.println("old age of Maggie: " + oldAge);
System.out.println();
linkedHashMap.forEach((name, age) -> System.out.println("name: " + name + " age: " + age));
      

LinkedHashMap<String, Integer> accessOrderMap = new LinkedHashMap<>(16, 0.5f, true);

System.out.println("Access order enabled...\n");

accessOrderMap.put("Rick", 52);
accessOrderMap.put("Carl", 32);
accessOrderMap.put("Rosita", 38);
accessOrderMap.put("Henry", 32);
accessOrderMap.put("Maggie", 33);
accessOrderMap.put("Negan", 45);

System.out.println("Rosita's age is " + accessOrderMap.get("Rosita"));
System.out.println("Maggie's age is " + accessOrderMap.get("Maggie"));

System.out.println();

accessOrderMap.forEach((name, age) -> System.out.println("name: " + name + " age: " + age));

System.out.println();

System.out.println("Updating map by changing Maggie's age and re ordering it as first entry: ");

System.out.println();

accessOrderMap.putFirst("Maggie", 27);
accessOrderMap.forEach((name, age) -> System.out.println("name: " + name + " age: " + age));
      

public class CountOccurrencesOfWords {

    public static void main(String[] args) {
        String text = "Good morning. Have a good class. " +
                "Have a good visit. Have fun!";

        Map<String, Integer> map = new HashMap<>();


        String[] words = text.split("[\\s+\\p{P}]");

        for (String word : words) {
            String key = word.toLowerCase();
            if (!key.isBlank()) {
                if (map.get(key) == null)
                    map.put(key, 1);
                else map.put(key, (map.get(key) + 1));
            }
        }

        System.out.printf("%-10s %10s\n", "Word", "Number of Occurrences");
        for (int i = 0; i < 40; i++)
            System.out.print("-");

        System.out.println();

        map.forEach((word, occurrences) -> System.out.printf("%-10s %10d\n", word, occurrences));
    }
}
        

public class CountOccurrencesOfKeywords {

    public static void main(String[] args) throws IOException {

        Map<String, Integer> map = prepareKeywordsMap();

        Scanner input = new Scanner(System.in);
        System.out.println("Enter java file path: ");
        String path = input.nextLine();

        File file = new File(path);

        if (!file.getName().matches(".+\\.java")){
            System.out.println("You should choose a java file");
            System.exit(0);
        }

        Scanner readFile = new Scanner(file);

        while (readFile.hasNext()){
            String line = readFile.nextLine();
            String[] words = line.split("\\s");

            for (String word : words) {
                if (map.containsKey(word)) {
                    int count = map.get(word);
                    map.put(word, ++count);
                }
            }
        }

        readFile.close();

        System.out.printf("%-10s %22s\n", "Keyword", "Number of Occurrences");
        for (int i = 0; i < 35; i++)
            System.out.print("-");

        System.out.println();

        map.forEach((keyword, occurrences) ->{
            if (occurrences != 0){
                System.out.printf("%-10s %10d\n", keyword, occurrences);
            }
        });
    }

    private static Map<String, Integer> prepareKeywordsMap(){
        String[] keywordString = {"abstract", "assert", "boolean",
                "break", "byte", "case", "catch", "char", "class", "const",
                "continue", "default", "do", "double", "else", "enum",
                "extends", "for", "final", "finally", "float", "goto",
                "if", "implements", "import", "instanceof", "int",
                "interface", "long", "native", "new", "package", "private",
                "protected", "public", "return", "short", "static",
                "strictfp", "super", "switch", "synchronized", "this",
                "throw", "throws", "transient", "try", "void", "volatile",
                "while", "true", "false", "null"};

        Map<String, Integer> map = new HashMap<>();

        for (String keyword : keywordString){
            map.put(keyword, 0);
        }

        return map;
    }
}