Quiz: Java Classes and Objects

5 questionsNo time limitPass: 60%+10 XP on first pass

Model real things with classes. Fields, constructors (default, parameterised, chaining), the this keyword, static members, getters/setters and toString().

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Question 1
What is true about a constructor?
It must return voidIt has the same name as the class and no return typeIt must be staticA class can have only one

Question 2

What does this print?

class A {
    static int count = 0;
    A() { count++; }
}
public class Main {
    public static void main(String[] args) {
        new A(); new A(); new A();
        System.out.println(A.count);
    }
}

130Error

Question 3
Why is this constructor buggy? Student(String name) { name = name; }
Constructors can't take parametersIt assigns the parameter to itself; the field stays nullIt should return a StudentStrings can't be assigned
Question 4
Which access modifier makes a field visible ONLY inside its own class?
publicprotectedprivatedefault (no modifier)
Question 5
Why can't a static method use an instance field directly?
Static methods are slowerIt runs without any object, so there is no "this" to read the field fromInstance fields are always privateJava forbids static methods