Apache Commons Math3探索之快速傅立叶变换代码示例

double inputData = new double[arrayLength]; // ... 给inputData赋值 FastFourierTransformer fft = new FastFourierTransformer(DftNormalization.STANDARD); Complex[] result = fft.transform(inputData, TransformType.FORWARD); 

import org.apache.commons.math3.transform.DftNormalization; import org.apache.commons.math3.transform.FastFourierTransformer; import org.apache.commons.math3.transform.TransformType; interface TestCase {   public Object run(List<Object> params) throws Exception;   public List<Object> getParams(); } class CalcFFT implements TestCase {   public CalcFFT()   {    System.out.print("本算例用于计算快速傅立叶变换。正在初始化 计算数据(" + arrayLength + "点)... ...");    inputData = new double[arrayLength];    for (int index = 0; index < inputData.length; index++)    {      inputData[index] = (Math.random() - 0.5) * 100.0;    }    System.out.println("初始化完成");   }   @Override   public List<Object> getParams()   {    return null;   }   @Override   public Object run(List<Object> params) throws Exception   {    FastFourierTransformer fft = new FastFourierTransformer(DftNormalization.STANDARD);    Complex[] result = fft.transform(inputData, TransformType.FORWARD);    return result;   }   private double[] inputData = null;   private final int arrayLength = 4 * 1024*1024; } public class TimeCostCalculator {   public TimeCostCalculator()   {   }   /**   * 计算指定对象的运行时间开销。   *   * @param testCase 指定被测对象。   * @return 返回sub.run的时间开销，单位为s。   * @throws Exception   */   public double calcTimeCost(TestCase testCase) throws Exception   {    List<Object> params = testCase.getParams();    long startTime = System.nanoTime();    testCase.run(params);    long stopTime = System.nanoTime();    System.out.println("start: " + startTime + " / stop: " + stopTime);    double timeCost = (stopTime - startTime) * 1.0e-9;    //   double timeCost = BigDecimal.valueOf(stopTime - startTime, 9).doubleValue();    return timeCost;   }   public static void main(String[] args) throws Exception   {    TimeCostCalculator tcc = new TimeCostCalculator();    double timeCost;    System.out.println("--------------------------------------------------------------------------");    timeCost = tcc.calcTimeCost(new CalcFFT());    System.out.println("time cost is: " + timeCost + "s");    System.out.println("--------------------------------------------------------------------------");   } }