Formatting double to 2 decimals doesn't work

Question

I want to round this double:

3.499999999999999

to:

3.50

And I already used these two methods:

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Answer 1

Your first solution is really, really close. Just do this:

    DecimalFormat df = new DecimalFormat("0.00");
    System.out.println(df.format(input));

The reason your version doesn't work is that you're taking the input double, formatting it as a String with 2dp, but then converting it back to a double. System.out.println is then printing the double as it always would, with no special decimal-place rules.