ArrayExamples.java

Below is the syntax highlighted version of ArrayExamples.java from §1.4 Arrays.

/******************************************************************************
 *  Compilation:  javac ArrayExamples.java
 *  Execution:    java ArrayExamples
 *
 *  Typical array processing code.
 *
 *  % java ArrayExamples 5
 *  a[]
 *  -------------------
 *  0.04851944273872377
 *  0.8311550808965679
 *  0.5288965750549762
 *  0.5053593215147596
 *  0.6162362251917868
 *
 *  a = [D@f62373
 *
 *  max = 0.8311550808965679
 *  average = 0.5060333290793628
 *
 *  b[]
 *  -------------------
 *  0.6162362251917868
 *  0.5053593215147596
 *  0.5288965750549762
 *  0.8311550808965679
 *  0.04851944273872377
 *
 *  dot product of a[] and b[] = 1.1795943990991937
 *
 ******************************************************************************/

public class ArrayExamples {
    public static void main(String[] args) {
        int n = Integer.parseInt(args[0]);

        // initialize to random values between 0 and 1
        double[] a = new double[n];
        for (int i = 0; i < n; i++) {
            a[i] = Math.random();
        }

        // print array values, one per line
        System.out.println("a[]");
        System.out.println("-------------------");
        for (int i = 0; i < n; i++) {
            System.out.println(a[i]);
        }
        System.out.println();
        System.out.println("a = " + a);
        System.out.println();

        // find the maximum
        double max = Double.NEGATIVE_INFINITY;
        for (int i = 0; i < n; i++) {
            if (a[i] > max) max = a[i];
        }
        System.out.println("max = " + max);


        // average
        double sum = 0.0;
        for (int i = 0; i < n; i++) {
            sum += a[i];
        }
        System.out.println("average = " + sum / n);

        // copy to another array
        double[] b = new double[n];
        for (int i = 0; i < n; i++) {
            b[i] = a[i];
        }

        // reverse the order
        for (int i = 0; i < n/2; i++) {
            double temp = b[i];
            b[i] = b[n-i-1];
            b[n-i-1] = temp;
        }

        // print array values, one per line
        System.out.println();
        System.out.println("b[]");
        System.out.println("-------------------");
        for (int i = 0; i < n; i++) {
            System.out.println(b[i]);
        }
        System.out.println();


        // dot product of a[] and b[]
        double dotProduct = 0.0;
        for (int i = 0; i < n; i++) {
            dotProduct += a[i] * b[i];
        }
        System.out.println("dot product of a[] and b[] = " + dotProduct);

    }

}