{"id":368,"date":"2017-05-19T15:00:14","date_gmt":"2017-05-19T13:00:14","guid":{"rendered":"http:\/\/antek.atthost24.pl\/?p=368"},"modified":"2017-05-19T01:05:48","modified_gmt":"2017-05-18T23:05:48","slug":"dzialanie-na-kilka-frontow-czyli-o-watkach-slow-kilka","status":"publish","type":"post","link":"https:\/\/blog.lantkowiak.pl\/index.php\/2017\/05\/19\/dzialanie-na-kilka-frontow-czyli-o-watkach-slow-kilka\/","title":{"rendered":"Dzia\u0142anie na kilka front\u00f3w – czyli o w\u0105tkach s\u0142\u00f3w kilka"},"content":{"rendered":"

Dzisiaj porozmawiamy sobie o dzia\u0142aniu na kilka front\u00f3w \ud83d\ude09 Czyli zobaczymy co to jest w\u0105tek i z czym to si\u0119 je \ud83d\ude42<\/p>\n

W tym wpisie zajmiemy si\u0119 g\u0142\u00f3wnie sposobami tworzenia w\u0105tk\u00f3w.<\/p>\n

Czym zatem jest ten w\u0105tek?<\/h3>\n

W\u0105tek<\/strong> jest niezale\u017cn\u0105 \u015bcie\u017ck\u0105 wykonania dzia\u0142aj\u0105c\u0105 w ramach procesu.<\/p>\n

Czym zatem jest proces? Proces<\/strong> jest to egzemplarz wykonywanego programu.<\/p>\n

Jak zatem widzimy w\u0105tek jest wykonywany w ramach procesu. W ramach jednego procesu mo\u017ce by\u0107 wykonywanych wiele w\u0105tk\u00f3w.<\/p>\n

Powinni\u015bmy r\u00f3wnie\u017c wiedzie\u0107, \u017ce w\u0105tki dziel\u0105 zasoby pomi\u0119dzy sob\u0105 w ramach jednego procesu, natomiast ka\u017cdy proces ma przydzielone swoje zasoby.<\/p>\n

W\u0105tki w Javie<\/h3>\n

W Javie w\u0105tki s\u0105 reprezentowane przez klas\u0119 Thread<\/strong>.<\/p>\n

Nowy w\u0105tek mo\u017cemy utworzy\u0107 w Javie na 3 sposoby:<\/p>\n

    \n
  1. Rozszerzaj\u0105c klas\u0119 Thread<\/strong><\/li>\n
  2. Implementuj\u0105c interfejs Runnable<\/strong><\/li>\n
  3. Implementuj\u0105c interfejs Callable<\/strong><\/li>\n<\/ol>\n

    Czym si\u0119 r\u00f3\u017cni\u0105 te podej\u015bcia?<\/p>\n

    Rozszerzenie klasy Thread<\/h4>\n

    Aby utworzy\u0107 w\u0105tek musimy rozszerzy\u0107 klas\u0119 Thread<\/strong> oraz nadpisa\u0107 metod\u0119 run<\/strong>.<\/p>\n

    public class MyThread extends Thread {\r\n\t@Override\r\n\tpublic void run() {\r\n\t\tSystem.out.println(\"Jestem watkiem!\");\r\n\t}\r\n}<\/pre>\n
    W metodzie run umieszczamy nasz kod, kt\u00f3ry zostanie wykonany w naszym nowym w\u0105tku.<\/p>\n
    Implementacja interfejsu Runnable<\/h4>\n
    Interfejs Runnable<\/strong> wymaga przez nas zaimplementowania jednej \u00a0metody – run<\/strong>.<\/p>\n
    public class MyThread implements Runnable {\r\n\t@Override\r\n\tpublic void run() {\r\n\t\tSystem.out.println(\"Jestem watkiem!\");\r\n\t}\r\n}<\/pre>\n
    Podobnie jak w poprzednim przypadku kod, kt\u00f3ry ma by\u0107 wykonany w w\u0105tku umieszczamy w metodzie run.<\/p>\n
    Implementacja interfejsu\u00a0Callable<\/h4>\n
    Interfejs Callable<\/strong> jest generyczny i dostarcza metod\u0119 call<\/strong>, kt\u00f3ra zwraca obiekt typu, kt\u00f3rego u\u017cyli\u015bmy przy implementacji Callable.<\/p>\n
    import java.util.concurrent.Callable;\r\n\r\npublic class MyThread implements Callable<String> {\r\n\t@Override\r\n\tpublic String call() throws Exception {\r\n\t\tSystem.out.println(\"Jestem watkiem i cos zwroce!\");\r\n\t\t\r\n\t\treturn \"Zwracana wartosc :)\";\r\n\t}\r\n}<\/pre>\n
    Tym razem kod, kt\u00f3ry ma si\u0119 wykona\u0107 w nowym w\u0105tku umieszczamy w metodzie call. Dodatkowo call wymusz\u0105 zwr\u00f3cenie obiektu. Zwr\u00f3\u0107my r\u00f3wnie\u017c uwag\u0119, \u017ce Callable deklaruje mo\u017cliwo\u015b\u0107 rzucenia wyj\u0105tku\u00a0kontrolowanego (checked exception).<\/p>\n
    Co wybra\u0107?<\/h3>\n
    Poznali\u015bmy 3 sposoby tworzenia w\u0105tk\u00f3w w Javie, ale kt\u00f3ry powinni\u015bmy u\u017cywa\u0107?<\/p>\n
    Sposobu pierwszego, czyli rozszerzania klasy Thread b\u0119dziemy prawdopodobnie u\u017cywa\u0107 najrzadziej. Musimy pami\u0119ta\u0107, \u017ce dziedziczenie powinno spe\u0142nia\u0107 warunek IS-A, czyli klasa pochodna powinna by\u0107 typem klasy nadrz\u0119dnej. Raczej rzadko b\u0119dziemy spotyka\u0107 si\u0119 z sytuacj\u0105 gdzie tworzona przez nas klasa b\u0119dzie musia\u0142a rozszerza\u0107 Thread, aby rozszerza\u0107 jej funkcjonalno\u015b\u0107. Wi\u0119cej o dziedziczeniu i kompozycji porozmawiamy w jednym z kolejnych wpis\u00f3w.<\/p>\n
    Czyli pozosta\u0142y nam dwie opcje Runnable i Callable. Tutaj powinni\u015bmy dokona\u0107 wyboru maj\u0105c na uwadze r\u00f3\u017cnice pomi\u0119dzy tymi interfejsami:<\/p>\n
      \n
    • metoda run<\/strong> z interfejsu Runnable jest typu void<\/strong>, natomiast metoda call<\/strong> z Callable zwraca wynik oblicze\u0144<\/strong><\/li>\n
    • metoda call<\/strong> pozwala zadeklarowa\u0107 wyj\u0105tki kontrolowane (checked exceptions), czego nie pozwala metoda run<\/strong>.<\/li>\n<\/ul>\n
      Podsumowanie<\/h3>\n
      Dzisiaj om\u00f3wili\u015bmy sposoby tworzenia w\u0105tk\u00f3w w Javie. Powinni\u015bmy zapami\u0119ta\u0107, \u017ce w\u0105tek mo\u017cemy stworzy\u0107 na 3 sposoby:<\/p>\n
        \n
      • rozszerzaj\u0105c klas\u0119 Thread,<\/li>\n
      • implementuj\u0105c interfejs Runnable,<\/li>\n
      • implementuj\u0105c interfejs Callable.<\/li>\n<\/ul>\n
        W nast\u0119pnym wpisie zwi\u0105zanym z w\u0105tkami om\u00f3wimy sposoby na uruchomienie i zarz\u0105dzanie naszymi w\u0105tkami.<\/p>\n","protected":false},"excerpt":{"rendered":"
        Dzisiaj porozmawiamy sobie o dzia\u0142aniu na kilka front\u00f3w \ud83d\ude09 Czyli zobaczymy co to jest w\u0105tek i z czym to si\u0119 je \ud83d\ude42 W tym wpisie zajmiemy si\u0119 g\u0142\u00f3wnie…<\/p>\n","protected":false},"author":1,"featured_media":372,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[12,7,23],"tags":[],"class_list":["post-368","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-dsp2017","category-java","category-watki"],"yoast_head":"\nDzia\u0142anie na kilka front\u00f3w - czyli o w\u0105tkach s\u0142\u00f3w kilka - Lukasz Antkowiak's blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/blog.lantkowiak.pl\/index.php\/2017\/05\/19\/dzialanie-na-kilka-frontow-czyli-o-watkach-slow-kilka\/\" \/>\n<meta property=\"og:locale\" content=\"pl_PL\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Dzia\u0142anie na kilka front\u00f3w - 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