/**

* Java. Level 2. Lesson 5. Example of homework

*

* @author Sergey Iryupin

* @version 0.2.3 dated Jan 14, 2018

*/

import java.util.Arrays;

class HW5Lesson {

final int SIZE = 10000000;

final int HALF_SIZE = SIZE / 2;

float testA65;

public static void main(String[] args) {

HW5Lesson hw = new HW5Lesson();

hw.doWithoutThreads();

hw.doWithThreads();

}

void doWithoutThreads() {

float[] arr = new float[SIZE];

Arrays.fill(arr, 1); // filling the array

long a = System.currentTimeMillis();

for (int i = 0; i < SIZE; i++)

arr[i] = (float)(arr[i] *

Math.sin(0.2f + i / 5) *

Math.cos(0.2f + i / 5) *

Math.cos(0.4f + i / 2));

System.out.println("Way 1 took " + (System.currentTimeMillis() - a));

testA65 = arr[HALF_SIZE + 65]; // getting control value

}

void doWithThreads() {

float[] arr = new float[SIZE];

float[] a1 = new float[HALF_SIZE];

float[] a2 = new float[HALF_SIZE];

Arrays.fill(arr, 1);

long a = System.currentTimeMillis();

System.arraycopy(arr, 0, a1, 0, HALF_SIZE);

System.arraycopy(arr, HALF_SIZE, a2, 0, HALF_SIZE);

Thread one = new Thread(new CalcArray(a1, 0));

Thread two = new Thread(new CalcArray(a2, HALF_SIZE));

one.start();

two.start();

try {

one.join();

two.join();

} catch (InterruptedException ex) {

ex.printStackTrace();

}

System.arraycopy(a1, 0, arr, 0, HALF_SIZE);

System.arraycopy(a2, 0, arr, HALF_SIZE, HALF_SIZE);

System.out.println("Way 2 took " + (System.currentTimeMillis() - a));

System.out.println(

Float.compare(testA65, arr[HALF_SIZE + 65]) == 0); // checking value

}

class CalcArray implements Runnable { // for threads

private float[] array;

private int shift;

CalcArray(float[] array, int shift) {

this.array = array;

this.shift = shift;

}

@Override

public void run() {

for (int i = 0; i < array.length; i++)

array[i] = (float)(array[i] *

Math.sin(0.2f + (i + shift) / 5) *

Math.cos(0.2f + (i + shift) / 5) *

Math.cos(0.4f + (i + shift) / 2));

}

}

}