[Java / array] [ ] や[ ][ ] とは

//配列を宣言
データ型[] 配列名

//example
int[] numbers;
String[] names;

//example
numbers = new int[4];
names = new String[3]; 

class Main {
  public static void main(String[] args) {
   int[] numbers = new int[5];
    numbers[0] = 5;
    numbers[1] = 20;
    numbers[2] = 100;
    numbers[3] = 2000;

   String[] mountains = new String[3];
    mountains[0] = "斜里岳";
    mountains[1] = "月山";
    mountains[2] = "蔵王山";

 }
}

System.out.println(numbers[0]);
System.out.println(mountains[2]);

//出力
5
蔵王山

//example
int[][] numbers;
String[][] mountains;

//example
numbers = new int[4][3];

//example
numbers[0][0] = 1;
numbers[1][1] = 100;
numbers[2][2] = 2000;
numbers[3][1] = 5000; 

//Example
  System.out.println(numbers[0][0]);
  System.out.println(numbers[2][2]);

//出力
1
2000