java.text.DecimalFormat::setRoundingMode does not round input as specified by the rounding mode.
Regression: Last worked in version 21.0.8.

Sample :
import java.math.RoundingMode;
import java.text.DecimalFormat;

public class DecimalFormatExample {
    public static void main(String[] args) {
        DecimalFormat format = (DecimalFormat) DecimalFormat.getInstance();
        format.setMaximumFractionDigits(10);
        format.setRoundingMode(RoundingMode.HALF_UP);
        var expected = "0.0000000001";
        var actual = format.format(Double.parseDouble("0.00000000005"));
        if (!expected.equals(actual)) {
            throw new AssertionError("Expected: " + expected + ", Actual: " + actual);
        }
    }
}

This bug happens on tie cases when DecimalFormat rounds a fractional double whose least significant digit is one index past the maximum fraction digits allowed by the format.