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I have a method in java that returns a double number and I want to compare every double number that is returned every time I call the method(say 5 times), so that I can conclude that the number returned is almost the same every time.
How can I do this?
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Using the == Operator As a result, we can't have an exact representation of most double values in our computers. They must be rounded to be saved. In that case, comparing both values with the == operator would produce a wrong result.
== should be used during reference comparison. == checks if both references points to same location or not. equals() method should be used for content comparison. equals() method evaluates the content to check the equality.
To compare two floating point or double values, we have to consider the precision in to the comparison. For example, if two numbers are 3.1428 and 3.1415, then they are same up to the precision 0.01, but after that, like 0.001 they are not same.
public static boolean almostEqual(double a, double b, double eps){ return Math.abs(a-b)<eps; } Where eps is measure of equality.
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You must first decide what "almost the same" means. For example, there's a method in java.lang.Math called ulp() which, given a double, returns the distance between that double and the next; i.e., the smallest possible difference between that number and any other. You might simply compare the difference between the two doubles and the result of calling that method.
On the other hand, maybe you want two numbers to just be within 1% of eachother. In that case, do the same computation, but use the first number multiplied by 0.01 instead of ulp() as the largest acceptable distance.
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