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POUsing Generics of Subclasses of Number to Create a Rollover Counter
 

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  1. POUsing Generics of Subclasses of Number to Create a Rollover Counter
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    <p>I'm trying to create a counter that will rollover whenever it reaches a preset ceiling and resets back to its floor value upon reaching said ceiling. I have implemented the class and it works just fine. However, on my way to my solution, I wanted to experiment with Java Generics. I want to try and extend my counter so that it doesn't only use integers, but instead can use any type of number. I know that counters typically call for just the use of integers anyway, but I wanted to see if it could be done.</p> <p>I figured that the code would be similar to below. However, java.lang.Number doesn't have a "generic" way of getting/setting its value. Do I need to create my own number class to enable this? Also, I know that if I do get this working, I need to alter my equals checks so that they have an error threshold for floating point values, this is more or less a modified version of my int counter with what I figured would work for generics.</p> <p><strong>Edit:</strong> It's been suggested that I take a mapping approach where I store an integer counter and keep a increment value so that when I want to spit out a number, I just multiply my current count by the increment value. However, I don't believe this will fill my exact needs because I don't want to necessarily increment by the same amount every time. The main focus of this counter is more of a way to have a fixed range number that, when added to or subtracted from, knows how to handle wrapping back around. </p> <p>I guess the best way to describe it (although probably improperly) would be like an <code>Integer</code> that automatically handles over/underflow.</p> <pre><code>package com.math; public class GenericRolloverCounter&lt;T extends Number&gt; { private T value; private T lowValue; private T highValue; public GenericRolloverCounter(T l_startValue, T l_highValue) { this.lowValue = l_startValue; this.highValue = l_highValue; this.value = l_startValue; } public T getValue() { return value; } public void setValue(T value) { this.value = value; } public void increment(T valToIncrementBy) { this.value += valToIncrementBy; if (this.value &gt; this.highValue) { this.value = (this.lowValue + (this.value - (this.highValue + 1))); } } public void increment() { this.increment(1); } public void decrement(T valToDecrementBy) { this.value -= valToDecrementBy; if (this.value &lt; this.lowValue) { this.value = ((this.value + this.highValue + 1) - this.lowValue); } } public void decrement() { this.decrement(1); } @Override public String toString() { return Integer.toString(this.value); } } </code></pre>
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    1. COWhat do you mean by any type of number? If you have a counter, and it's at 5.54643643, what do you expect the next number to be?
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    2. COThere's a reason we use integers for counting things. Because integers are... countable. There is no notion of a "next real number". There IS a notion of a next double, but it's rather arbitrary and the gaps between doubles is not uniform.
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    3. CO@Cruncher As kids we all learn to "count by 5's" and it suggests we don't always count in single integral amounts. For example, we count money in units of .01 and .05 and .10 and .25 in the US, since that's the way our coins are divided into US dollars. I don't think its the concept of having a next double so much as incrementing and decrementing by a fixed amount or set of amounts.
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      1. USLee Meador
 

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