#Java Callback

1 messages · Page 1 of 1 (latest)

scenic zephyr
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Hi there, I am coding a little Java stuff for my school, and I can't seem to find anything online to help. I want to use a callback function as sort of rich-code (we do not need to do it) because i repeat loops a bunch. I want to sort of reference or callback this function or set of commands again time after time. Something like in the callback of Javascript if that helps. Thanks!

ember hawkBOT
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<@&987246399047479336> please have a look, thanks.

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Here is an AI assisted attempt to answer your question 🤖. Maybe it helps! In any case, a human is on the way 👍. To continue talking to the AI, you can use </chatgpt:1108714622413963314>.

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the traditional way). Can you please explain how to use callback functions in Java?

wise kelp
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Mind posting some psudo code to better explain what you mean?

shut verge
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taking an argument whose type is a Functional Interface is the modern convention in Java.

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public void someMethod(String foo, IntSupplier callback) {
   ...
   int v = callback.getAsInt();
}

Here I've used IntSupplier as the type of the callback. This interface provides an int getAsInt() method.

it could be called using a lambda or a method reference.

String s = "abc";
String t = "Some other String";

someMethod(s, () -> t.length());
someMethod(s, t::length);
ember hawkBOT
#

@scenic zephyr

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scenic zephyr
shut verge
#

I'm not sure what callbacks have to do with repeating moves. Are you just wanting to repeating those loops? That's just a regular method.

private static void setAndMove(Googa g, int x, int y) {
   g.setPosition(x, y);
   for (int i = 0; i < 5; i++) {
       g.turnRight();
       g.move();
   }
}

...

Googa g = new Gogga();
setAndMove(g, 1, 1);
setAndMove(g, 9, 1);
setAndMove(g, 9, 9);
setAndMove(g, 1, 9);
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Far more interesting would be a Move interface that can compose some base operations.

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Note: this ignores defensive copies and bounds checks and is formatted for brevity.

interface Gogga {
    void move();
    void turnLeft();
    void turnRight();
}

@FunctionalInterface interface Action {
    public static Action repeat(Action action, int count) {
        return g -> {
            for (int i = 0; i < count; i++) { action.run(g); }
        };
    }

    public static Action of(Action... actions) {
        return g -> {
            for (Action action : actions) { action.run(g); }
        };
    }

    void run(Gogga g);
}

enum StandardAction implements Action {
    MOVE() { @Override public void run(Gogga g) { g.move(); } },
    TURN_LEFT() { @Override public void run(Gogga g) { g.turnLeft(); } },
    TURN_RIGHT() { @Override public void run(Gogga g) { g.turnRight(); } };
}

class GoggaTest implements Gogga {
    @Override public void move() { System.out.println("Move"); }
    @Override public void turnLeft() { System.out.println("Left"); }
    @Override public void turnRight() { System.out.println("Right"); }
}

...

var test = new GoggaTest();
var action = Action.of(Action.repeat(Action.of(StandardAction.TURN_RIGHT, StandardAction.MOVE), 3), StandardAction.TURN_LEFT);

action.run(test);

Prints something like...

Right
Move
Right
Move
Right
Move
Left
scenic zephyr
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I dont want to have some really messy code thats just a bunch of repeats, id much rather just like callback to something and the code does it for me yk?

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and i really dont know much about what is written there xd

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could you explain? briefly so you dont have to like say paragraphs, i feel bad xd

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i dont want to copy code yk, i want to learn it so i can put it to use and during like a test i i can save time, im not trying to do this to get marks, all the stuff we do i know already lol, just tryna do some extra cause im interested in learning java too

shut verge
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How is a 'callback' different from the method approach? What are you trying to achieve that would make a callback useful?

scenic zephyr
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i wanna use less lines of code, because it gets really messy

wise kelp
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I think you're asking how you can split your code up into methods and re-use them, callbacks is something else

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talden is right in his example and in the screenshot you provided, you're repeating code that you want to avoid

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so if you take his example, he's created a method that does your repeated looping logic

# 
private static void setAndMove(Googa g, int x, int y) {
   g.setPosition(x, y);
   for (int i = 0; i < 5; i++) {
       g.turnRight();
       g.move();
   }
}
``` (the code he provided)
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now in your screenshot, all the code that has this ```java
g.setPosition(x, y);
for (int i = 0; i < 5; i++) {
g.turnRight();
g.move();
}

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can be replaced with simply, setAndMove(g, 1, 1); (update the values as needed)

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If you're struggling to understand this code, it might be worth doing some research into methods/functions in java

scenic zephyr
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oh, i guess im being stupid, i thought callbacks were the same in java script xd

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thank youuu

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sorry for being so hard to work with xd

wise kelp
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they should be the same but even in javascript, they're different to what you're asking here lol