allocate same memory for one class or changing final variable in java

Question

I have a class in android (java) I forced to create that class every second (new className() ) because variable is final . this use a lot of memory . I can not change the class because it is implemented in a library

I want : when at first create className and OS allocates a memory place, when I create my class again , it replace to that place which allocated at the first time. Or How I can change final variable?

then dont create new instances, instate design your class so that it can mutate! — ΦXocę 웃 Пepeúpa ツ, May 24 '17 at 05:50
What does the class do? Depending on its responsibilities, you might want to use either a singleton (as @RandykaYudhistira suggested above) or the flyweight design pattern. — Riaan Nel, May 24 '17 at 05:50
@ΦXocę 웃 Пepeúpa ツ I can not chang that class, that class is defined in library — Telegram Instagram, May 24 '17 at 05:52
You can't explicitly deallocate memory in Java. If there are no more references to an object it should be automatically garbage collected. If that's not happening, there may be a memory leak in your code or the library you're using. — shmosel, May 24 '17 at 06:01
it is my problem that when garbage collected automatically , my app became slow — Telegram Instagram, May 24 '17 at 06:03
No idea what you are asking for. If it is "your class", why does it matter that it is in a library? Sorry, but you rather give some code here. — GhostCat, May 24 '17 at 06:32

score 1 · Answer 1 · answered May 24 '17 at 06:29

1

Singleton Class example :

public class SomeClass {
  private static LibraryClass libraryClass;
  public static LibraryClass getInstance() {
    if(libraryClass == null) {
      libraryClass = new LibraryClass();
    }
    return libraryClass;
  }
}

Then you can call it : LibraryClass libraryClass = SomeClass.getInstance();

answered May 24 '17 at 06:29

Randyka Yudhistira

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I want to set a value to final variable in libraryclass and I set value only in constructor, in your example I can not set value to variable – Telegram Instagram May 24 '17 at 06:39
@TelegramInstagram if that value fixed at the beginning it's trivial to adapt constructor invocation in snippet above. If that value changes, since it's `final`, you cannot reuse the instance. – Hugues M. May 24 '17 at 07:06

score 0 · Answer 2 · answered May 24 '17 at 05:53

0

You can write a reset() method on your class, which resets all fields of the object to the initial state.

When you want to create a new object, without creating a new object, call reset() on old object and re-use it.

answered May 24 '17 at 05:53

Lahiru Chandima

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I can not change the class because it is implemented in a library – Telegram Instagram May 24 '17 at 05:55
@TelegramInstagram, if the class has setters for all fields, you can write a utility method `resetObject(LibObject object)` in your code which calls setters of all fields of the object to reset them to initial value. Then, you can call this method when you want to re-use the object. – Lahiru Chandima May 24 '17 at 05:57
it is my problem taht I can not write(set) method in that class, and variables is final , I can not change class at all . – Telegram Instagram May 24 '17 at 06:01
@TelegramInstagram, you may be able to set values of private final fields of this object with the method described in following answer. https://stackoverflow.com/a/3301720/1015678 – Lahiru Chandima May 24 '17 at 06:16
@LahiruChandima Good point. Does that work on Android too? (I mean the technique to bypass `final` linked in previous comment, not your answer ☺) – Hugues M. May 24 '17 at 07:09

Telegram Instagram · Accepted Answer · 2017-05-27T07:40:18.663

0

I solved my problem:

By this code:

Field modifierslatitude = className.class.getDeclaredField("latitude");
modifierslatitude.setAccessible(true);
modifierslatitude.set(classNameObjectThatFirstCreate, location.getLatitude() + MainActivity.y * 0.0002);

in fact I changed final variable without create new class again and again

edited May 27 '17 at 07:40

answered May 24 '17 at 08:17

Telegram Instagram

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OMG. OMG. OMG. OMG. OMG. – G. Blake Meike May 26 '17 at 03:27
@TelegramInstagram You are a hacker! – G. Fiedler May 30 '17 at 10:38

allocate same memory for one class or changing final variable in java

3 Answers3