question: public String toString ( ) { StringBuffer sb = new StringBuffer ( ) ; char [ ] separator = { '[' , ' ' } ; int n = rows . length ; for ( int i = 0 ; i < n ; i ++ ) { separator [ 0 ] = '{' ; for ( int j = 0 ; j <= i ; j ++ ) { sb . append ( separator ) ; sb . append ( rows [ i ] [ j ] ) ; separator [ 0 ] = ' ' ; } sb . append ( '}' ) ; sb . append ( '\n' ) ; } return sb . toString ( ) ; }
target:  Returns a string representation of the system.