[20210312] (Java) Arrays toString(), deepToString(), instanceof, isInstance(), char to int

[JuHyun419]

Arrays toString(), deepToString()

• 1차원 배열 값 출력할때 for문 사용했었는데, toString()으로 바로 출력
• deepToString -> 2차원 배열 이상 출력

import java.util.Arrays;

public class Test {

    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 5};
        System.out.println(Arrays.toString(arr));

        int[][] arr2 = {{1, 2}, {3, 4, 5}};
        System.out.println("toString: " + Arrays.toString(arr2));
        System.out.println("deepToString: " + Arrays.deepToString(arr2));

        int[][][] arr3 = {{{1, 2}, {3, 4, 5}}};
        System.out.println(Arrays.deepToString(arr3));
    }
}

[1, 2, 3, 4, 5]
toString: [[I@5d5eef3d, [I@56f4468b, [I@6cc4c815]
deepToString: [[1, 2], [3, 4, 5]]
deepToString: [[[1, 2], [3, 4, 5]]]

instanceof vs isInstance()

• instanceof : 컴파일시 타입 체크
• isInstance(): 런타임시 타입 체크

## char to int - char - '0'

        char ch = '1';
        char ch2 = '9';
        System.out.println(ch - '0');
        System.out.println(ch2 - '0');

1
9