[SOLVED] I don't know how to implement math.round() or any other solution to get ##.## in JTextField

I don't know how to implement math.round() or any other solution to get ##.## in JTextField

I am displaying average in JTextField, and I want to round it up to two decimal places to use my code below, to create BarChart using JFreeChart. I have seen many tutorials about that, but I don't know how to implement any of it in my code.

That is my list:

List<Double> light = new ArrayList<Double>();
for (Measurement measurement : readMeasurements) {
light.add(Double.parseDouble(measurement.getLight()));}

double averageLight = Utils.calculateAverage(light);
textLight.setText(averageLight+" ...");

That is my Utils that calculate average:

public static double calculateAverage(List<Double> list){
        double av=0;
        double sum=0;
        
        for(double value : list){
            sum+=value;
            
        }
        av = sum/list.size();
        return av;
    }

With that I get in textfiled output like ##.################.

And here is part of code that creates BarChart using JFreeChart. It works when in JTextField output is ##.##:

String temperature = textTemp.getText();
String light = textLight.getText();
String vcc = textVcc.getText();
                
DefaultCategoryDataset dataset = new DefaultCategoryDataset();
dataset.setValue(new Double (temperature), "Measurements", "Temperature");
dataset.setValue(new Double (light), "Measurements", "Light");
dataset.setValue(new Double (vcc), "Measurements", "Vcc");

How can I make any changes to that code to make an output in JTextField like ##.##?

Solution

textLight.setText(String.format("%.2f", averageLight));

The "%.2f" is a format string, and means "format an argument as a floating point number with two decimal places". For more detail on what characters you can use in one of those, and what they each mean, refer to http://docs.oracle.com/javase/7/docs/api/java/util/Formatter.html