Ex)
int [][] score = new int[4][3]; // 선언 및 생성
int [][] arr = new int[][] { {1,2,3}, {4,5,6} }; //초기화1
int [][] arr = { {1,2,3}, {4,5,6} }; //초기화2
int[][] score = new int[5][];
score[0] = new int[4];
score[1] = new int[3];
score[2] = new int[2];
score[3] = new int[2];
score[4] = new int[3];
java의 정석 chapter5