5.1 Java基本数据类型
long //64bit
int //32bit
short //16bit
char //16bit
byte //8bit
boolean //1bit
float //32bit
double //64bit
数组的声明
int[] week;
week=new int[7];
int[] week={1,2,3,4,5,6,7};
int[][] num={{1,2,3,4},{5,6,7,8}};
int[][] num=null;
num=new int[3][];
num[0]=new int[4];
num[1]=new int[3];
num[2]=new int[5];
num.length;//数组行数
num[0].length;//第一行元素的个数
num[2].length;
int[][][] a={{{5,1},{6,7}},{{9,4},{8,3}}};