The challenge
Create a method take that accepts a list/array and a number n, and returns a list/array array of the first n elements from the list/array.
If you need help, here’s a reference:
https://docs.oracle.com/javase/6/docs/api/java/util/Arrays.html#copyOfRange(int[],%20int,%20int)
Test cases
import org.junit.Test;
import static org.junit.Assert.assertArrayEquals;
import org.junit.runners.JUnit4;
import java.util.*;
public class SolutionTest {
@Test
public void basicTests() {
assertArrayEquals("should return the first 3 items", new int[]{0, 1, 2}, ZywOo.take(new int[]{0, 1, 2, 3, 5, 8, 13}, 3));
assertArrayEquals("should return 0 items", new int[0], ZywOo.take(new int[]{0, 1, 2, 3, 5, 8, 13}, 0));
assertArrayEquals("empty array should return empty array", new int[0], ZywOo.take(new int[0], 3));
}
@Test
public void randomTests() {
for (int i = 0; i < 100; i++) {
int n = (int)Math.floor(100 * Math.random());
int[] randomArray = generateRandomArray();
assertArrayEquals("Testing with array " + Arrays.toString(randomArray) + " and n = " + n, solution(randomArray, n), ZywOo.take(randomArray, n));
}
}
private int[] solution(int[] arr, int n) {
return arr.length > 0 && arr.length > n ? Arrays.copyOfRange(arr, 0, n) : arr;
}
private int[] generateRandomArray() {
int length = (int)Math.floor(100 * Math.random());
int min = (int)Math.floor(-100 * Math.random());
int max = (int)Math.floor( 100 * Math.random());
return new Random().ints(length, min, max).toArray();
}
}
The solution in Java
Option 1:
public class ZywOo {
public static int[] take(int[] arr, int n) {
if (arr.length==0) return arr;
if (n>arr.length) return arr;
int[] arr2 = new int[n];
for (int i=0; i<n; i++) {
arr2[i] = arr[i];
}
return arr2;
}
}
Option 2 (using copyOf):
import java.util.Arrays;
class ZywOo {
static int[] take(int[] arr, int n) {
return n > arr.length ? arr : Arrays.copyOf(arr, n);
}
}
Option 3 (using streams):
import java.util.Arrays;
public class ZywOo {
public static int[] take(int[] arr, int n) {
return Arrays.stream(arr).limit(n).toArray();
}
}
Option 4 (using copyOfRange):
import java.util.Arrays;
public class ZywOo {
public static int take(int[] arr, int n)[] {
return Arrays.copyOfRange(arr, 0, Math.min(arr.length, n));
}
}