gistfile1.java

public class Lagrange {
    interface LagrangeFun {
        double  computate(double x);
    }

    public static LagrangeFun interpolate(final double[] x, final double[] y,final int n){
        return new LagrangeFun() {
            @Override
            public double computate(double argx) {
                double c, s=0;
                for (int i=0; i<n; i++)
                {
                    c=1;
                    for (int j=0; j<n; j++)
                    {
                        if (i!=j)   c*=(argx-x[j])/(x[i]-x[j]);
                    }
                    s+=c*y[i];
                }
                return s;
            }
        };
    }
}

public class HelloLambda {
    public static void main(String[] args) {
        double[] xs = new double[10];
        double[] ys = new double[10];
        int i,j;
        for(i=0,j=-5,xs[i]=j; i<10;i++)
            ys[i] = j*j;
        Lagrange.LagrangeFun y_pow_x = Lagrange.interpolate(xs,ys,10);
        for(i=-50; i<=50;i++)
            System.out.println(y_pow_x.computate(i));
    }
}