parsing - Simple "If-Then-Else" descent parser in Java (homework) -

there's no code snippets around web shows how parse ambiguos "if-then-else" grammar (at least pseudo code worth)

in following grammar (upper-case non terminals, quoted terminals , other symbols regular expressions done both terminals , terminals)

stats ::= (stat)* stat ::= if_stat if_stat ::= "if" exp "then" stat ("else" stat)? | exp exp ::= ident ident ::= ('a'-'z''a'-'z')+ 

the if statement ambiguos infact following code

if if b c else d 

can readed both as

if then{     if b          c     else         d } 

or

if then{     if b         c } else     d 

now. disambiguating seems simple (given did correctly):

stats ::= (stat)* stat ::= if_stat if_stat ::= "if" exp "then" stat |              "if" exp "then" if_stat_ex "else" stat |              exp if_stat_ex ::= "if" exp "then" if_stat_ex "else" if_stat_ex |              exp exp ::= ident ident ::= ('a'-'z''a'-'z')+ 

however i'm failing write working parser correctly parse following test cases (each line different test)

//input                                 //expected output if x if y z else w            if x (if y z else w) if x y else if z w else k     if x y else (if z w else k) if x y else if y w            if x y else (if y w ) if x if y z else w else k     if x (if y z else w) else k 

here's small class reproducing i'm missing.

public class parser{      public list<stat> parsestats(){         list<stat> stats = new list<>();         while(tokenizer.hastokens())             stats.add(parseif());         return stats;     }      private stat parseif(){         // todo: here?     }      private exp parsecond(){         exp condition = parseident();         tokenizer.consume( "then" );         return condition;     }      private exp parseident(){         final ident name = new ident( tokeziner.tostring());         tokenizer.moveonnexttoken();         return name;     } }