Getting a lot of "method cannot be applied to (java.lang.string)"

I am trying to write a program that simulates a simple libraray. I am having some trouble applying some of the methods to the main method.

Here is my code so far:

public class Library {
	Book[] books;
	int numBooks;
	String address;

void addBook(Book b) { //Adds books to the array of this library
	books[numBooks] = b;
	numBooks++;
	}
public boolean borrowBook(Book aBook) { //Marks the book as borrowed  
         return aBook.borrowed(); //refers to a method in another class I created 
     }  
   
public boolean returnBook(Book aBook) { //Marks the book as returned  
         return aBook.returned();  
     }

public Library(String street) { //creates new street address
	street = address;
}

public String printAddress() { //returns the street address when referenced
return address;
}

public Book printAvailableBooks(Book b) { //supposed take a book out of the list if borrowed
for(numBooks = 0; numBooks < 10; numBooks++) {
	if (numBooks>0) {
		System.out.println("Were sorry there are no books avalible at this library");
	}
	else if(b.borrowed == false) { //references a varible in the Book class
		System.out.println("We are sorry this book is checked out."); //this line is supposed to be java.lang.string
	}
	else if(b.borrowed == true) {
	System.out.println(b[numBooks]);
				}
			}
	return b;}

public String printOpeningHours(String hours) {
	hours = "We are open from 9-5.";	
}

public static void main(String[] args){

Library firstLibrary = new Library("10 Main St."); // Create two libraries
Library secondLibrary = new Library("228 Liberty St.");

firstLibrary.addBook(new Book("The Da Vinci Code"));// Add four books to the first library
firstLibrary.addBook(new Book("Le Petit Prince"));
firstLibrary.addBook(new Book("A Tale of Two Cities"));
firstLibrary.addBook(new Book("The Lord of the Rings"));

System.out.println("Library hours:"); // Print opening hours and the addresses
printOpeningHours();
System.out.println();

System.out.println("Library addresses:");
firstLibrary.printAddress();
secondLibrary.printAddress();
System.out.println();
// Try to borrow The Lords of the Rings from both libraries
System.out.println("Borrowing The Lord of the Rings:"); 
firstLibrary.borrowBook("The Lord of the Rings"); 
firstLibrary.borrowBook("The Lord of the Rings"); 
secondLibrary.borrowBook("The Lord of the Rings"); 
System.out.println();

// Print the titles of all available books from both libraries
System.out.println("Books available in the first library:");

System.out.println(firstLibrary.printAvailableBooks(firstLibrary.Book));

System.out.println("Books available in the second library:");
System.out.println(secondLibrary.printAvailableBooks());
// Return The Lords of the Rings to the first library
System.out.println("Returning The Lord of the Rings:"); 
firstLibrary.returnBook("The Lord of the Rings"); 
System.out.println();

// Print the titles of available from the first library
System.out.println("Books available in the first library:" + firstLibrary.printAvailableBooks()); 
 
	}

}

Here are the main errors that I am getting:

borrowBook(Book) in Library cannot be applied to (java.lang.String)
firstLibrary.returnBook("The Lord of The Rings")

printAvailbleBooks(Book) in Library cannot be applied to ()
System.out.println(secondLibrary.printAvailableBook())

array required but Book found
System.out.println(b[numBooks])

a non-static method printOpeningHours() cannot be referenced from a static context
printOpeningHours()

Also the borrow and return book methods reference another method in my book class.

How can I fix these errors?

and

How could I write this code so that it will mark a book as borrowed and print out "Sorry that book is checked out" when ever someone tries to borrow it again?

Thanks a lot,
Brian

How can I fix these errors?

Simply, you are not calling your methods with the correct type of parameters. For example, your returnBook() method takes a Book object, yet you pass it a String object. To fix it, pass a Book object. Or modify your method to take a String object.

Henry

Thanks for replying. Ok, so I tried to insert book into my methods so that: firstLibrary.returnBook(Book("The Lord of the Rings")); . Now it is telling me that the symbol for Book isn't found. I though this was the proper return type?

I have also tried to change it to firstLibrary.borrowBook(books[1]); and it is telling me a "non-static varible cannot be referenced from a static context".

Brian Wimpsett wrote:Thanks for replying. Ok, so I tried to insert book into my methods so that: firstLibrary.returnBook(Book("The Lord of the Rings")); . Now it is telling me that the symbol for Book isn't found. I though this was the proper return type?

Book is a class -- not a method. What is it that you are trying to do?

Henry

Brian Wimpsett wrote:I have also tried to change it to firstLibrary.borrowBook(books[1]); and it is telling me a "non-static varible cannot be referenced from a static context".

That error message pretty much explains itself. You cannot access an instance variable from a static method -- as a static method doesn't have access to an instance (this reference).

Henry

Thanks, Henry. I fixed my code and it compiled. Excuse me for keeping this thread open, I am pretty new at Java. When I ran it it throws the run time error of : java.lang.NullPointer. at Library.addBook(Library.java:10) ; at Library.main(Library.java:60). I looked online and this exception was caused with an illegal use of null. Like if you try to divide a null variable with a number.

Why is it telling me this?

Anyways, here is my final code:

public class Library {
	static Book[] books;
	int numBooks;
	String address;
	static String hours;

void addBook(Book b) { //Adds books to the array of this library
	books[numBooks] = b;
	numBooks++;
	}
public boolean borrowBook(Book aBook) { //Marks the book as borrowed  
         return aBook.borrowed(); //refers to a method in another class I created 
     }  
   
public boolean returnBook(Book aBook) { //Marks the book as returned  
         return aBook.returned();  
     }

public Library(String street) { //creates new street address
	street = address;
}

public String printAddress() { //returns the street address when referenced
return address;
}

public Book printAvailableBooks() { //supposed take a book out of the list if borrowed
for(numBooks = 0; numBooks < 10; numBooks++) {
	if (numBooks>0) {
		System.out.println("Were sorry there are no books avalible at this library");
	}
	else if(books[numBooks].borrowed() == false) { //references a varible in the Book class
		System.out.println("We are sorry this book is checked out."); //this line is supposed to be java.lang.string
	}
	else if(books[numBooks].borrowed() == true) {
	System.out.println(books[numBooks]);
				} 
	continue;
			}
	return books[numBooks];}

static String printOpeningHours() {
	hours = "We are open from 9-5.";
	return hours;	
}

public static void main(String[] args){

Library firstLibrary = new Library("10 Main St."); // Create two libraries
Library secondLibrary = new Library("228 Liberty St.");

firstLibrary.addBook(new Book("The Da Vinci Code"));// Add four books to the first library
firstLibrary.addBook(new Book("Le Petit Prince"));
firstLibrary.addBook(new Book("A Tale of Two Cities"));
firstLibrary.addBook(new Book("The Lord of the Rings"));

System.out.println("Library hours:"); // Print opening hours and the addresses
printOpeningHours();
System.out.println();

System.out.println("Library addresses:");
firstLibrary.printAddress();
secondLibrary.printAddress();

// Try to borrow The Lords of the Rings from both libraries
System.out.println("Borrowing The Lord of the Rings:"); 
firstLibrary.borrowBook(books[1]); 
firstLibrary.borrowBook(books[1]); 
secondLibrary.borrowBook(books[1]);

// Print the titles of all available books from both libraries
System.out.println("Books available in the first library:");

System.out.println(firstLibrary.printAvailableBooks());

System.out.println("Books available in the second library:");
System.out.println(secondLibrary.printAvailableBooks());
// Return The Lords of the Rings to the first library
System.out.println("Returning The Lord of the Rings:"); 
firstLibrary.returnBook(books[1]);

// Print the titles of available from the first library
System.out.println("Books available in the first library:" + firstLibrary.printAvailableBooks()); 
 
	}

}

Thank you for your patience,
Brian

I looked online and this exception was caused with an illegal use of null. Like if you try to divide a null variable with a number.

Whatever site that you "looked online", please don't use that site again -- as the explanation is a bunch of gibberish.

When I ran it it throws the run time error of : java.lang.NullPointer. at Library.addBook(Library.java:10) ; at Library.main(Library.java:60).

Follow the trace -- look at the addBook() method at line 10 of Library.java. Basically, null pointer exceptions are caused when you try to use something that doesn't exist. Which is this case, tried to use an array that you never instantiated. Just look at the line, and you should easily see which variable you are trying to use.

Henry

Ok. I am kind of lost. I am not sure how my variable for addBook is wrong. I am creating a new instance of the book class like my method addBook is supposed to do. I tried to remove static on my books varible and I also removed void and it is still giving me the nullPointer exception. How do I change my constructor or variable so that it builds an array?

the problem isn't that you didn't create the book object it is that you are trying to add it to an array you haven't created yet.

You declared the reference to the array but never created the array object.

hmm... Why isn't this piece of code creating the array? :

Brian Wimpsett wrote:hmm... Why isn't this piece of code creating the array? :

Maybe you can start with the Sun tutorial on arrays...

http://java.sun.com/docs/books/tutorial/java/nutsandbolts/arrays.html

Henry

Brian Wimpsett wrote:hmm... Why isn't this piece of code creating the array?

Does the following create a Book object?

Book b;