java - String HashTable Implementation -

for assignment need create hashtable of strings, i've created 1 using integers , works perfectly, i'm running trouble now.

i keep getting java.lang.numberformatexceptions inputted strings , i'm not sure why happening. here's code using hashtable class;

public class hashtable {     private sortedlist[] hasharray;     private int arraysize;      public hashtable(int size) {         arraysize = size;         hasharray = new sortedlist[arraysize];          for(int = 0; < arraysize; i++) {             hasharray[i] = new sortedlist();         }     } // end hashtable()      public void displaytable() {         for(int = 0; < arraysize; i++) {             system.out.print(i + ". ");             hasharray[i].displaylist();         }     } // end displaytable()      public int hash(string key) {         int hashkey = integer.parseint(key);         return hashkey % arraysize;     } // end hash()      public void insert(link link) {         string key = link.getkey();         int hashval = hash(key);         hasharray[hashval].insert(link);     } // end insert()      public void delete(string key) {         int hashval = hash(key);         hasharray[hashval].delete(key);     } // end delete() } // end hashtable 

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this code list:

public class sortedlist {     private link first;      public void sortedlist() {         first = null;     } //end sortedlist()      public void insert(link link) {         string key = link.getkey();         link previous = null;         link current = first;          while(current != null && key.compareto(current.getkey()) > 0) {             previous = current;             current = current.getnext();         }          if(previous == null) {             first = link;         } else {             previous.setnext(link);             link.setnext(current);         }     } // end insert()      public void delete(string key) {         link previous = null;         link current = first;          while(current != null && !key.equals(current.getkey())) {             previous = current;             current = current.getnext();         }          if(previous == null) {             first = first.getnext();         } else {             previous.setnext(current.getnext());         }     } // end delete()      public link find(string key) {         link current = first;           while(current != null && current.getkey().compareto(key) <= 0) {             if(current.getkey().equals(key)) {                  return current;             }             current = current.getnext();         }         return null;     } // end find()      public void displaylist() {         system.out.print("list (first -> last): ");         link current = first;         while(current != null) {             current.displaylink();             current = current.getnext();         }         system.out.println();     } // end displaylist() } //end sortedlist() 

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the link class basic one, thrown error on line:

        int hashkey = integer.parseint(key); 

in hash function, in hashtable class.

edit: understand being asked do, need convert string integer, , perform hash function index position.

because link.getkey() , key variables in hashtable.insert , hashtable.delete allow strings passed. should using

public int hash(string key) {     int hashkey = key.hashcode();     return hashkey % arraysize; } // end hash()