Arrays.md

Arrays

1D array

Default initialization

int n = 5; // number of items
int[] num = new int[n];

With initial values

import java.util.Arrays;

int n = 5; // number of items
int[] num = new int[n];

Arrays.fill(num, -1);

With fixed initial values

int[] num = {1, 2, 3, 4};

Sort an array in ascending order

import java.util.Arrays;

int[] nums = { 4, 5, 9, 1};

Arrays.sort(nums);

Print an array

int[] nums = {4, 5, 9, 1};
System.out.println(num);

for (int n : nums) {
    System.out.println(n);
}

Length of an array

int[] num = {5, 2, 3};
int len = num.length;

2D array

With fixed initial values

int[][] nums = {
    {1, 2},
    {3, 4},
    {5, 6}
};

Sort an array in ascending order

import java.util.Arrays;

Arrays.sort(nums, (b,a) -> Integer.compare(b[0], a[0]));

Sort an array in descending order

Arrays.sort(nums, (b,a) -> Integer.compare(a[0], b[0]));

Print an array

for (int[] num : nums){
    for (int n : num){
        System.out.print(n + " ");
    }
    System.out.println();
}