java - Use 2 methods 1. Check if object exists 2. Add object -

i wondering how go create 2 methods, 1. checking, if object exists within array (based on 1 of parameters). 2. secondly add method allows user / me add objects array when previous (1st method) returns false.

here try:

public class book {     string name;     int isbn;       public book(string e, int inr) throws libraryexception{         if(e.equals("")){             throw new libraryexception("blank / empty name not allowed!");         }          else if(inr < 1 || inr > 9000){             throw new libraryexception("the isbn number outside allowed range (1 - 9000)! ");         }         setname(e);         setisbn(inr);     }       public boolean equals(object obj){         if(obj instanceof book){             isbn = (isbn)obj;             return true;         }         return false;     }       public string getname() {         if(name == null || name == ""){             system.out.print("does not exist!");         }         return name;     }      public void setname(string name) {         this.name = name;     }      public int getisbn() {         if(isbn < 0){             system.out.print("isbn (libri) exception added!");         }         return isbn;     }      public void setisbn(int isbn) {         this.isbn = isbn;     } } 

.

public class library {     string name;     book[] books;     int nrbooks = 0;      public library(string name, int nrbooks) throws libraryexception {           if(name.equals("")){             throw new libraryexception("blank names not allowed");         }          if(nrbooks < 500){             throw new libraryexception("the number of books needs greater 500!");         }          this.name = name;         this.nrbooks = nrbooks;         this.books = new book[nrbooks];      }       public void addbook(book book) throws libraryexception {          if(indexof(book) == -1){                 if(nrbooks < books.length)                     books[nrbooks++] = book;           }     }     private int indexof(book book)throws libraryexception {          if(nrbooks < book[].length){          }           return -1;     }      public static void main(string[]args) throws libraryexception{         library b = new library("sami frasheri", 700);         b.addbook(new book("paul colhen - alchemist", 1));         b.addbook(new book("paul colhen - winners stand alone", 2));         b.addbook(new book("paul colhen - river piedra sat , cried", 3));          system.out.print(b);     } } 

tried arraylist in java?.

they able solve of problems facing. have @ contains , add.

please note, must override hashcode , equals method of book object work effectively.