Java: Simple BigDecimal logical error

Question

I've got a simple piece of code that isn't behaving as it should.

This piece of code is attempting to add an array of BigDecimals to then divide by array.length to find an average. However, the first phase of the algorithm fails to add the arrays together correctly (in the variable "sum").

public BigDecimal getAverageHeight()
{
    BigDecimal sum = new BigDecimal(0);
    BigDecimal[] heights = getAllHeights();

    for (int a = 0; a < heights.length; a++)
    {
        sum.add(heights[a]);
        System.out.println("Height[" + a + "] = " + heights[a]);
        System.out.println("Sum = " + sum.setScale(2, BigDecimal.ROUND_HALF_UP));
    }        

    return sum.divide(new BigDecimal(heights.length));
}

The output is as follows:

Height[0] = 24  
Sum = 0.00  
Height[1] = 24  
Sum = 0.00  
Height[2] = 24  
Sum = 0.00  
Height[3] = 26  
Sum = 0.00  
Height[4] = 26  
Sum = 0.00  
Height[5] = 26  
Sum = 0.00

I'm sure its a simple error, but I'm getting tired of starring at the problem, thanks in advance.

Answer 1

BigDecial.add() returns the sum, it does not alter it. Do this:

sum = sum.add(heights[a]);