OCA Java SE 7 Programmer I Certification Guide

class Book {
    String ISBN;
    Book(String val) {
        ISBN = val;
    }
}
class TestEquals {
    public static void main(String... args) {
        Book b1 = new Book("1234-4657");
        Book b2 = new Book("1234-4657");
        System.out.print(b1.equals(b2) +":");
        System.out.print(b1 == b2);
    }
}

	a true:false
	b true:true
	c false:true
	d false:false
e Compilation error—there ...