You can do both (if System.out.println("Your number was " + median); is not working you have something else wrong. Show us the stack trace). printf allows you some more formatting options (such as the number of decimal places) without having to use a DecimalFormat, but it is a choice on style rather than anything else.

Personally I find string concatenation easer on the eyes and easer to maintain. The %blah gets lost in the string, errors in string concatenation is a compile time error and adding a new variable requires less thought. However I'm in the minority on this.

The pros in printf is that you don't need to construct a bunch of formatters, others find its format easer on the eyes and when using a printf like method provided by a logging framework the string building only happens if actually required.

double value = 0.5;
System.out.println("value: " + value);
System.out.printf("value: %f", value);

If you want to set a number of decimal places:

    double value = 0.5;
    // String concatenation 
    DecimalFormat df = new DecimalFormat("0.000");
    System.out.println("value: " + df.format(value));

    // printf
    System.out.printf("value: %.3f", value);

You can also use %g as well to round-off and print double as integer:

System.out.printf("x=%g%n", x);