context free grammar - Java Implementation of an algorithm for CFG in Chomsky form -

the goal convert pseudo code actual working code. thought had figured out there's not quite right.

the rule i'm using is

s -> rt|empty t -> tr|a r => tr|b 

here's pseudo code:

d == "on input w == wi . ..wn : 1. if w == e , s -> e rule, accept. [handle w == empty case] 2. == 1 n: [examine each substring of length 1]  3.     each variable a: 4.         test whether -> b rule, b == wi.  5.         if so,place in table(i,i).  6. l == 2 n: 7.     == 1 n -l + 1: 8.         let j == + l - 1, 9.         k == j -1: 10.            each rule \037 bc: 11.            if table(i,k)contains b , table(k + 1,j)contains                c,put in table(i,j). 12.if s in table(l,n), accept.otherwise, reject. 

here's actual code:

public class algorithm {  public static void main(string[] args){     string w = " abab";     string table[][] = new string[w.length()][w.length()];     if (w.isempty()){         system.out.println("accept\n");     }      for(int i=1; i<w.length();i++){         if(w.charat(i)=='a')             table[i][i]="r";         else if(w.charat(i)=='b')             table[i][i]="t";     }     for(int l=2; l<=w.length();l++){         for(int i=1; i<w.length()-l+1;i++){             int j = i+l-1;             for(int k=i; k<=j-1;k++){                 if(table[i][k].contains("t") && table[k+1][j].contains("r"))                     table[i][j]="t,r"; //not sure how part?                 else if(table[i][k].contains("r") && table[k+1][j].contains("t"))                     table[i][j]="s";              }         }      }     system.out.println("finished");     system.out.println(w);     for(int i=1;i<w.length();i++){         for(int j=1;j<w.length();j++){         system.out.print(table[i][j]+"\t");}         system.out.println("");      }     //system.out.println((table[1][w.length()-1]));     //if (table[1][w.length()-1].equals("s"))     //  system.out.println("accept"); }  } 

i get:

 abab    r    s   s   null        null t   t,r s       null null    r   s       null null    null    t 

however can tell, baba can derived grammar.

figured out did wrong. first off had <= rather < secondly didn't initialize array entirely null references @ points.