String s="gsdhgjsjsgdjh";int a=s.length();//一定要有括号;int a[]={45,5,8,45,21,6,68,4,8}int b=a.length;//没有括号偶;b=9.int a[]={{45,25},{89,6,7,1},{6,89,1},{9,6,2,1,2}};int b=a.length//b=4,int c=a[0].length// c=2int d=a[3].length//d=5;;