Thread: What is Wrong When calling the function using arrayList.

code for library.java

import java.util.ArrayList;
public class Library {
private String libraryName,libAddress;
Library(String libraryName,String libAddress)
{
this.libraryName = libraryName;
this.libAddress =libAddress;

}
public String getLibraryName() {
return libraryName;
}
public void setLibraryName(String libraryName) {
this.libraryName = libraryName;
}
public String getLibAddress() {
return libAddress;
}
public void setLibAddress(String libAddress) {
this.libAddress = libAddress;
}
ArrayList<Book> bookList = new ArrayList<Book>();
ArrayList<Member> memberList = new ArrayList<Member>();

public void addBook(Book book)
{
bookList.add(book);

}

public void bookInfo()
{
for (int i=0; i< bookList.size(); i++)
{
System.out.println("Author of " +bookList.get(i).getName()+" is "+bookList.get(i).getAuthorName());
}
}
public void getBookLend(String bookName) //function call to check the name of person to whom book is issued
{

System.out.println(bookName);

for(Book boo : bookList)
if(bookName.equals(boo.getName()))
{
System.out.println("In Loop "+boo.getName());
System.out.println(boo.getNameOfPerson());
System.out.println("Book Issued To " +boo.getNameOfPerson()); //ERROR HERE. GETTING NULL WHY???

}
}
}


code for member.java



import java.util.ArrayList;

public class Member {
String memberName;
int id;
ArrayList<Member> memberList = new ArrayList<Member>();
public Member(String memberName, int id) {
this.memberName = memberName;
this.id = id;
}

public String getMemberName() {
return memberName;
}
public void setMemberName(String memberName) {
this.memberName = memberName;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public ArrayList<Member> getMemberList() {
return memberList;
}
public void setMemberList(ArrayList<Member> memberList) {
this.memberList = memberList;
}
public void addMember(Member member)
{
memberList.add(member);

System.out.println(member.memberName +" added Successully as a member");
}
public void showMember()
{
for(Member member : memberList)
System.out.println(member.getMemberName());
}

}



Code for book.java






public class Book {
private String name,authorName,catagory;
private int noOfCopies,bookId;
private String nameOfPerson;
Book(String name ,int bookId,String authorName,String catagory,int noOfCopies)
{
this.name =name;
this.authorName=authorName;
this.catagory =catagory;
this.noOfCopies = noOfCopies;

}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAuthorName() {
System.out.println("nutan");
return authorName;
}
public void setAuthorName(String authorName) {
this.authorName = authorName;
}
public String getCatagory() {
return catagory;
}
public void setCatagory(String catagory) {
this.catagory = catagory;
}
public int getNoOfCopies() {
return noOfCopies;
}
public void setNoOfCopies(int noOfCopies) {
this.noOfCopies = noOfCopies;
}
public String getNameOfPerson() {
return nameOfPerson;
}
public void setNameOfPerson(String nameOfPerson) {
this.nameOfPerson = nameOfPerson;
}
public void bookLend(int bookId,String nameOfPerson) //function called when a book is issued
{

if(noOfCopies == 0)
System.out.println("Non Applicable");
else
{
noOfCopies--;
this.nameOfPerson = nameOfPerson;
this.setNameOfPerson(this.nameOfPerson);
System.out.println("book issued to \t"+getNameOfPerson() +"\t");
System.out.println("Number Of Available copies \t" +noOfCopies);
}
}

}

Code for Execution.java



public class Execution {
public static void main(String[] args) {

Library lib = new Library("Universal Library","MUMBAI"); //Library Constructor
Book book1 = new Book("Book Java",1,"Scmidt","computers",1);
Book book2 = new Book("C++",2,"Bjarne","computers",6); //Book Objects
Book book3 = new Book("C",3,"Yaswant","computers",4);
Book book4 = new Book("Adobe Basics",4,"Mr.","basics",3);
Book book5 = new Book("Learning",5,"Paul","english",2);
Book book6 = new Book("How To?",6,"Ravi","vhut",1);
Member member1 = new Member("nn", 01);
Member member2 = new Member("ri", 02); //Members objects
lib.addBook(book1);
lib.addBook(book2);
lib.addBook(book3); //calling addBook function to add books in the list
lib.addBook(book4);
lib.addBook(book5);
lib.addBook(book6);
member1.addMember(member1);
member2.addMember(member2);
book6.bookLend(6,"nu"); //function to issue books
lib.getBookLend("C++"); // function call to find out whom book is issued
}
}

I don't think that anybody will be bothered to compile and run all that stuff. What compiler errors do you get? What runtime Exceptions do you get? Post the full error messages.

Originally Posted by PhHein

I don't think that anybody will be bothered to compile and run all that stuff. What compiler errors do you get? What runtime Exceptions do you get? Post the full error messages.

Ya i know... there are no compiling errors... the output which i m getting of System.out.println("Book Issued To " +boo.getNameOfPerson()); in library.java is null... Just call the getBookLend() method in Execution.java .... please help me.

Ok. You have six different books. You have two members.
book6.bookLend(6,"nu"). Book "How to?" is lend to a person "nu" , who isn't even a member.
lib.getBookLend("C++"); -> NULL, because no member has that book.

Everything is good. Your code works as expected.

--- Update ---

Another one: do the books lend themselves (book6.bookLend) , or rather the library (lib.bookLend(bookName, memberName))?

means i have to create bookLend method inside the Library..............

and thanks for your help..

It would be more intuitive to me.