ArrayExampleTest.java

package com.examplehub.basics.array;

import static org.junit.jupiter.api.Assertions.*;

import java.util.Arrays;
import org.junit.jupiter.api.Test;

class ArrayExampleTest {
  @Test
  void testInit() {
    int[] nums = {1, 2, 3, 4, 5};
    assertEquals("[1, 2, 3, 4, 5]", Arrays.toString(nums));

    nums = new int[] {1, 2, 3};
    assertEquals("[1, 2, 3]", Arrays.toString(nums));
  }

  @Test
  void testReadWrite() {
    int[] nums = {1, 2, 3, 4, 5};
    assertEquals(1, nums[0]);
    assertEquals(2, nums[1]);
    assertEquals(3, nums[2]);
    assertEquals(4, nums[3]);
    assertEquals(5, nums[4]);

    for (int i = 0; i < nums.length; ++i) {
      assertEquals(i + 1, nums[i]);
    }

    for (int i = nums.length - 1; i > 0; --i) {
      assertEquals(i + 1, nums[i]);
    }

    nums[0] = 0;
    assertEquals(0, nums[0]);

    try {
      nums[nums.length] = 1;
      fail(); /* wont' execute it */
    } catch (IndexOutOfBoundsException indexOutOfBoundsException) {
      assertTrue(true);
    }

    try {
      nums[-1] = 1;
      fail(); /* wont' execute it */
    } catch (IndexOutOfBoundsException indexOutOfBoundsException) {
      assertTrue(true);
    }
  }

  @Test
  void testLength() {
    int[] nums = {1, 2, 3, 4, 5};
    assertEquals(5, nums.length);
    nums = new int[] {};
    assertEquals(0, nums.length);
  }

  @Test
  void testTravelUsingFor() {
    int[] nums = {1, 2, 3, 4, 5};
    int count = 1;
    for (int num : nums) {
      assertEquals(count++, num);
    }
  }

  @Test
  void testToString() {
    int[] nums = {1, 2, 3, 4, 5};
    assertEquals("[1, 2, 3, 4, 5]", Arrays.toString(nums));
  }

  @Test
  void testStringArray() {
    String[] company = {"Google", "Facebook", "Amazon", "Microsoft"};
    assertEquals("Google", company[0]);
    assertEquals("Facebook", company[1]);
    assertEquals("Amazon", company[2]);
    assertEquals("Microsoft", company[3]);
    assertEquals('g', company[0].charAt(3));
    assertEquals("[Google, Facebook, Amazon, Microsoft]", Arrays.toString(company));
  }

  @Test
  void tesTwoDimensionalArray() {
    int[][] twoDimensionalNumbers = {
      {1, 2, 3},
      {4, 5, 6, 7},
      {8, 9},
      {10, 11, 12, 13, 14, 15}
    };
    assertEquals(4, twoDimensionalNumbers.length);

    assertEquals(3, twoDimensionalNumbers[0].length);
    assertEquals(4, twoDimensionalNumbers[1].length);
    assertEquals(2, twoDimensionalNumbers[2].length);
    assertEquals(6, twoDimensionalNumbers[3].length);

    assertEquals(9, twoDimensionalNumbers[2][1]);
    int count = 1;
    for (int i = 0; i < twoDimensionalNumbers.length; ++i) {
      for (int j = 0; j < twoDimensionalNumbers[i].length; ++j) {
        assertEquals(count++, twoDimensionalNumbers[i][j]);
      }
    }

    count = 1;
    for (int[] twoDimensionalNumber : twoDimensionalNumbers) {
      for (int num : twoDimensionalNumber) {
        assertEquals(count++, num);
      }
    }

    assertEquals("[1, 2, 3]", Arrays.toString(twoDimensionalNumbers[0]));
    assertEquals("[4, 5, 6, 7]", Arrays.toString(twoDimensionalNumbers[1]));
    assertEquals("[8, 9]", Arrays.toString(twoDimensionalNumbers[2]));
    assertEquals("[10, 11, 12, 13, 14, 15]", Arrays.toString(twoDimensionalNumbers[3]));
    assertEquals(
        "[[1, 2, 3], [4, 5, 6, 7], [8, 9], [10, 11, 12, 13, 14, 15]]",
        Arrays.deepToString(twoDimensionalNumbers));
  }

  @Test
  void testSort() {
    int[] nums = {1, 3, 5, 7, 9, 2, 4, 6, 8, 10};
    Arrays.sort(nums);
    assertEquals("[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]", Arrays.toString(nums));
  }
}