Meaning of delta or epsilon argument of assertEquals for double values in java

Meaning of delta or epsilon argument of assertEquals for double values in java

In Java, the assertEquals method is often used in testing frameworks like JUnit to compare expected and actual values. When comparing double or float values using assertEquals, you might come across two additional parameters: delta or epsilon. These parameters are used to specify a tolerance level for comparing floating-point numbers, which are susceptible to small inaccuracies due to how they are stored in memory.

Here's what these parameters mean:

  1. delta (for assertEquals in JUnit):

    • delta is a parameter used in JUnit's assertEquals method to specify the maximum allowable absolute difference between the expected and actual values.
    • If the absolute difference between the expected and actual values is within the specified delta, the assertion passes.
    • It's particularly useful when comparing floating-point numbers because small rounding errors can occur during calculations.

    Example:

    double expected = 0.1 + 0.2; // The actual result is slightly different due to floating-point precision double actual = 0.3; double delta = 0.0001; // Tolerance level assertEquals(expected, actual, delta); // Passes because the absolute difference is within the delta

  2. epsilon (for custom comparisons):

    • epsilon is a more general term used in computer science and mathematics to represent a very small value (usually close to zero).
    • In the context of comparing floating-point numbers, epsilon refers to a small value that is used as a tolerance or margin of error when checking for equality.
    • When manually comparing floating-point numbers, you can use epsilon to decide how close two numbers must be to consider them equal, taking into account the precision of your numeric calculations.

    Example:

    double num1 = 0.1 + 0.2; // The actual result is not exactly 0.3 due to precision issues double num2 = 0.3; double epsilon = 1e-10; // A small value to represent the tolerance boolean equal = Math.abs(num1 - num2) < epsilon; // Check if the absolute difference is within epsilon if (equal) { System.out.println("The numbers are considered equal within epsilon."); } else { System.out.println("The numbers are not considered equal within epsilon."); }

In summary, delta is a parameter in JUnit's assertEquals method specifically used for comparing expected and actual values with a specified tolerance, while epsilon is a more general concept used to define a small value for custom comparisons, especially when dealing with floating-point numbers and precision issues. Both delta and epsilon help handle the limitations of comparing floating-point values due to their inherent imprecision.

More Tags

null-check sqlplus automationanywhere twitter-bootstrap-2 dom-events git-checkout amazon-swf mat-pagination x-axis blazor-webassembly

More Java Questions

More Geometry Calculators

More Tax and Salary Calculators

More Various Measurements Units Calculators

More Organic chemistry Calculators