Mine

// MInteger stands for Mutable Integer and is simple class that has one int field.

Core talib = new Core();
MInteger outBegIdx = new MInteger();
MInteger outNbElement = new MInteger();
double[] output = new double[data.length];
talib.rsi(0, data.length-1, data, period, outBegIdx, outNbElement, output);
return output;