Arrays in Java

Basics

int [] intArray = {0,0,0,0,0} 
int [] intArray = new int[5] // same as above, initializes to 0
 
int[] intArray;
intArray = new int[5]; // 크기 5의 빈 배열
 
int[] intArray = {1, 2, 3, 4, 5};

Useful

• length
  • getting the length of array
• Arrays.toString(array)
  • Changes the array to string

int[] arr = {1,2,3,4,5};
System.out.println(arr.length); // 5
Arrays.sort(arr);
System.out.println(Arrays.toString(arr));

Nested arrays

int[][] arr = {{1,2,3}, {4,5,6}};
System.out.println(arr[1][2])
 
// change value
arr[1][2] = 7;
System.out.println(arr[1][2]); // 7

Aliasing

int[] arr1 = {1,2,3,4,5};
int[] arr2 = arr1;

• arr1 and arr2 point to the same address, so arr2 is an alias to arr1

Cloning

int[] arr1 = {1, 2, 3, 4, 5};
int[] arr2 = arr1.clone();
 
arr1[0] = 100;
System.out.println(arr1[0]); // 100
System.out.println(arr2[0]); // 1

For-each

for (int i : intArray)
{
	System.out.println(i);
}

• X getting the index but the element itself

Different ways of creating arrays

List.of

• Makes it immutable

List<String> list = List.of("A", "B", "C");

Arrays.asList(...)

• Fixed-size List backed by an array

List<String> list = Arrays.asList("A", "B", "C");

new ArrayList<>()

• Mutable List

List<String> list = new ArrayList<>(Arrays.asList("A", "B", "C"));