How to Prevent Variable Subtraction During Object Collision in Java Game Development

Learn how to effectively manage variable changes during object interactions in your Java game. Discover techniques to control subtraction timing and improve gameplay.
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This video is based on the question https://stackoverflow.com/q/68047325/ asked by the user 'leo.rocket' ( https://stackoverflow.com/u/16267658/ ) and on the answer https://stackoverflow.com/a/68047419/ provided by the user 'BeUndead' ( https://stackoverflow.com/u/2478398/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Stopping Variable Subtraction for a Few Seconds in Java

As a newcomer to Java programming, especially in game development, you may encounter situations where you need to manage object interactions carefully. For instance, you may be working with two objects that are moving towards each other, and each time they collide, a variable representing their life or health should be decremented. However, in certain cases, you want to ensure that this health is only reduced once within a specified timeframe, rather than continuously whenever they touch.

The Problem

In the provided Java code, the health variable leben is being reduced every time the objects touch, which can lead to unintended rapid loss of health. You want to establish a mechanism to only subtract health once during each collision event and prevent further reductions for a short period. This is where a cooldown mechanism comes into play.

Original Code Overview

Let's take a look at the initial approach:

[[See Video to Reveal this Text or Code Snippet]]

In this example, there is a boolean flag touching that allows health to be deducted only once as long as the objects touch. However, this approach does not account for any cooldown period, leading to multiple subtractions if the objects remain in contact.

Solution Using Cooldown Mechanism

To solve this problem, we can implement a cooldown counter that only allows the health to be decremented after a specified cooldown has expired. Here’s how we can modify the code:

Step-by-Step Solution

Introduce a Cooldown Variable:
Create an integer variable that keeps track of how many frames have passed since the last health decrease.

Check Cooldown Before Subtraction:
At the beginning of the damage method, verify if the cooldown variable is greater than zero. If it is, decrement it and exit the method early.

Decrement Health and Reset Cooldown:
Only if the object is touching and the cooldown is at zero should you reduce the health by 1 and set the cooldown counter.

Revised Code Example

Here’s an implementation of the above steps:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By introducing a cooldown mechanism, you can maintain a smoother and more predictable gameplay experience where a variable is only affected once during a specific interaction. This simple adjustment prevents rapid health loss and keeps the game balanced.

Always remember to test and adjust the cooldown duration to find what works best for your game mechanics!



This technique not only improves gameplay but also enhances your code's readability and maintainability. As you continue your journey in Java game development, don't hesitate to explore and implement more such patterns!