How can I use functional programming to do string manipulation?

Question

I'm writing a function where I'm essentially doing the same thing over and over. I have the function listed below

public String buildGarmentsString(List<Garment> garments)
{
    StringBuilder garmentString = new StringBuilder(10000);
    for(int i=0;i<4;i++)
    {
        garmentString.append(this.garmentProductId(i,garments.get(i).getProductId()));
        garmentString.append(this.garmentColor(i,garments.get(i).getColor()));
        for(int j=0;j<garments.get(i).getSizes().size();j++)
        {
            //check xxsml
            if(garments.get(i).getSizes().get(j).getXxsml() >0)
            {
                garmentString.append(this.garmentSizes(i, Size.xxsml(),garments.get(i).getSizes().get(j).getXxsml()));

            }

            //check xsml
            if(garments.get(i).getSizes().get(j).getXsml() > 0)
            {
                garmentString.append(this.garmentSizes(i,Size.xsml(),garments.get(i).getSizes().get(j).getXsml()));
            }

            //check sml
            if(garments.get(i).getSizes().get(j).getSml() > 0)
            {
                garmentString.append(this.garmentSizes(i,Size.sml(),garments.get(i).getSizes().get(j).getSml()));
            }

            //check med
            if(garments.get(i).getSizes().get(j).getMed() > 0)
            {
                garmentString.append(this.garmentSizes(i,Size.med(),garments.get(i).getSizes().get(j).getMed()));
            }

            //check lrg
            if(garments.get(i).getSizes().get(j).getLrg() > 0)
            {
                garmentString.append(this.garmentSizes(i,Size.lrg(),garments.get(i).getSizes().get(j).getLrg()));
            }

            //check xlrg
            if(garments.get(i).getSizes().get(j).getXlg() > 0)
            {
                garmentString.append(this.garmentSizes(i,Size.xlg(),garments.get(i).getSizes().get(j).getXlg()));
            }

            //check xxlrg
            if(garments.get(i).getSizes().get(j).getXxl() >0)
            {
                garmentString.append(this.garmentSizes(i,Size.xxlg(),garments.get(i).getSizes().get(j).getXxl()));
            }

            //check xxxlrg
            if(garments.get(i).getSizes().get(j).getXxxl() >0)
            {
                garmentString.append(this.garmentSizes(i,Size.xxxlg(),garments.get(i).getSizes().get(j).getXxxl()));
            }


        }
    }
}

This is my garmentSizes function:

public String garmentSizes(int garmentNumber, String size,int numberToSend)
{
    String garmentSizes = "&garment["+garmentNumber+"][sizes]["+size+"]="+numberToSend;
    return garmentSizes;
}

I'm trying to figure out how I can get this done with a lot less code. I've read that with functional programming you can do things like pass in functions to parameters to other functions. After doing some reading online, I think I want to do something like this but I'm not sure how or what the best approach would be.

I have done some reading here on stack overflow and I've seen people mention using either the Command pattern or FunctionalJava or LambdaJ for trying to approximate this feature in Java. I've read over the documentation for the two libraries and read the Wikipedia Article on the Command Pattern, but I'm still not sure how I would use any of those to solve my particular problem. Can somebody explain this to me? As somebody that has never done any functional programming this is a bit confusing.

Answer 1

• You could use local variables to decrease the amount of repetition. Say bySize = garments.get(i).getSizes().get(j) for example.
• instead of size.getXxsml(), size.getXsml() etc. you could use an enum for sizes and loop on sizes.

The whole thing would then look like:

for(int j=0;j<garments.get(i).getSizes().size();j++) {
    bySize = garments.get(i).getSizes().get(j);
    for (Size s : Size.values()) {
        if (bySize.get(s) > 0)  {
            garmentString.append(garmentSizes(i, s, bySize.get(s)));
        }
    }
}

The bySize.get(s) method could be implemented either with a switch that directs to the right method or directly in the enum and you could get rid of the getXsml etc. methods.