Question

1. What is output by the following code:

ArrayList< Integer > a = new ArrayList< Integer >();
ArrayList b = a;
a.add(new Integer(4));
b.add(new Integer(5));
a.add(new Integer(6));
a.add(new Integer(7));
System.out.println(b.size());

A)1

B)2

C)3

D)4

E)5

2. Assume the Student and Employee classes each extend the Person class. The Student class overrides the getMoney method in the Person class. Consider the following code:

    Person p1, p2, p3;
    int m1, m2, m3;

    p1 = new Person();
    m1 = p1.getMoney();     // assignment 1

    p2 = new Student();
    m2 = p2.getMoney();     // assignment 2

    p3 = new Employee();
    m3 = p3.getMoney();     // assignment 3

The reference to getMoney in assignment 2 is to the ________ class.

A)Child

B)Person

C)Student

D)Employee

E)this cannot be determined by examining the code

3. Assume the Student and Employee classes each extend the Person class. The Student class overrides the getMoney method in the Person class. Consider the following code:

    Person p1, p2, p3;
    int m1, m2, m3;

    p1 = new Person();
    m1 = p1.getMoney();     // assignment 1

    p2 = new Student();
    m2 = p2.getMoney();     // assignment 2

    p3 = new Employee();
    m3 = p3.getMoney();     // assignment 3

The reference to getMoney in assignment 3 is to the ________ class.

A)Child

B)Employee

C)Person

D)Student

E)this cannot be determined by examining the code

4. Consider the following code:

ArrayList< Integer > a = new ArrayList< Integer >();
int value;
a.add(4);
a.add(5);
a.add(new Integer(6));
value = a.size();
System.out.println(value);

What happens when this code is compiled?

A)A compiler error occurs on Line 1, because you cannot instantiate an ArrayList in this way.

B)A compiler error occurs on Line 3, because you cannot add an int to an ArrayList< Integer >.

C)A compiler error occurs on Line 5, because the keyword new is missing when adding an Integer.

D)A compiler error occurs on Line 6, because value must be declared as an Integer.

E)This code compiles without errors.

5. Consider the following incomplete class:

public class SomeClass
{
    public static final int VALUE1 = 30;
    public static int value2 = 10;
    private int value3 = 5;
    private double value4 = 3.14;

    public static void someMethod()
    {
        // implementation not shown
    }

    public void someOtherMethod()
    {
        // implementation not shown
    }
}

Which variable is accessible without instantiating a SomeClass object?

A)VALUE1

B)VALUE1 and value2

C)value2

D)value3

E)None of the above

6. Consider the following incomplete class:

public class SomeClass
{
    public static final int VALUE1 = 30;
    public static int value2 = 10;
    private int value3 = 5;
    private double value4 = 3.14;

    public static void someMethod()
    {
        // implementation not shown
    }

    public void someOtherMethod()
    {
        // implementation not shown
    }
}

The method someMethod is defined as static. This means

A)the method is an accessor method

B)the method is accessible outside SomeClass

C)the method is not accessible outside SomeClass

D)the method is accessible without instantiating a SomeClass object

E)the method is accessible only by using a previously instantiated SomeClass object

7. Consider the following incomplete class:

public class SomeClass
{
    public static final int VALUE1 = 30;
    public static int value2 = 10;
    private int value3 = 5;
    private double value4 = 3.14;

    public static void someMethod()
    {
        // implementation not shown
    }

    public void someOtherMethod()
    {
        // implementation not shown
    }
}

The variable VALUE1 is defined as public static final. This means

A)the variable can be changed

B)the variable is an instance variable

C)the variable is not accessible outside SomeClass

D)the variable is a constant and cannot be changed

E)the variable should not be named using all capital letters

8. Which of the following describes an overridden method?

A)One of several methods in a class with the same name but different parameter lists

B)One of several methods in a class with the same name but different return values

C)A method in a subclass with the same method heading as a method in a parent class

D)Any method that invokes super();

E)A method that contains a call to itself

9. All classes in Java are directly or indirectly subclasses of the _______ class.

A)Object

B)Reference

C)String

D)this

E)Wrapper

10. Consider the following code:

public class B1
{
     private int i;
     private int j;
     …
}

public class B2 extends B1
{
     private int m;
     private int n;
     …
}

public class B3 extends B2
{
     private int z;
     …
}

Which of the following is true regarding the use of instance variable j in class B1?

A)It is directly accessible only in B1

B)It is directly accessible only in B2

C)It is directly accessible only in B3

D)It is directly accessible in B1 and B2

E)It is directly accessible in B1, B2, and B3

11. Consider the following code:

public class B1
{
     private int i;
     private int j;
     …
}

public class B2 extends B1
{
     private int m;
     private int n;
     …
}

public class B3 extends B2
{
     private int z;
     …
}

Which of the following sets of instance variables are directly accessible in class B3?

A)i, j, m, n

B)i, j, m, n, z

C)i, j, z

D)m, n, z

E)z

12. Consider the following code:

public class A1
{
    public int x;
    private int y;
    …
}

public class A2 extends A1
{
    public int a;
    private int b;
    …
}

public class A3 extends A2
{
    private int q;
    …
}

Which of the following sets of instance variables are directly accessible in class A2?

A)a, b

B)x, a, b

C)x, y, a, b

D)x, y, a, b, q

E)y, a, b

13. Consider the following code:

public class A1
{
    public int x;
    private int y;
    …
}

public class A2 extends A1
{
    public int a;
    private int b;
    …
}

public class A3 extends A2
{
    private int q;
    …
}

Which of the following sets of instance variables are directly accessible in class A3?

A)a, b, q

B)a, q

C)x, a, b, q

D)x, a, q

E)x, y, a, b, q

14. Consider the following client code and assume that it compiles successfully.

public class MainClass
{
    public static void main(String[] args)
    {
        SomeClass myObject = new SomeClass(4, 5);

        int fred = SomeClass.SOME_VALUE;
        int barney = myObject.method1();
        int wilma = SomeClass.method2(4);
    }
}

Which of the following is a static variable?

A)method1

B)method2

C)SomeClass

D)SOME_VALUE

E)This cannot be determined by examining the above code

15. The relationship between a child (sub) class and a parent (super) class is referred to as a(n) ____ relationship.

A)abstract

B)has-a

C)is-a

D)polymorphism

E)was-a

Answer 1

Question1

Ans) Option D(answer is 4)

Explanation:-

• Here we declare an array list 'a' of integer.
• Then copy array b =a.
• So adding values in a is same in b.
• So after insertion of values in a,its size increment to 4
• So the copy of a is b, is also increment.
• So b.size = 4.

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Question 2

Ans) Option C(Student class)

Explanation:-

• Student class is the child class of Person class.
• In assignment 2 Person p instantiate the object of student
• So call Student method

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Question 3

Ans) Option B(Employee class)

Explanation:-

• Employee class is the child class of Person class.
• In assignment 3 Person p instantiate the object of Employee
• So call Employee method

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Question 4

Ans) Option E ( no compilation error)

Explanation:-

• Code will work perfectly and will get output = 3.
• Here we declare an array list as integer
• So add directly an integer or instantiated integer value are added in the array list properly
• So size increases to 3
• No error happen

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Question 5

Ans) Option B (VALUE1 and value2)

Explanation:-

• In java static variables can access without instantiation of class object.

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Question 6

Ans) Option D ( The method is accessible without instantiating a SomeClass object )

Explanation:-

• In java static method can access without instantiation of class object.

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Question 7

Ans) Option D ( The variable is a constant and cannot be changed )

Explanation:-

• final is the keyword used for constants in java.
• It cannot be changed.

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Question 8

Ans) Option c( A method in a subclass with the same method heading as a method in a parent class )

Explanation:-

• A method is said to be overriden,it has the same name and parametres and return type as the method in parent class.

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Question 9

Ans) Option A (Object)

Explanation:-

• In java all classes have a parent class.
• In classes do not have a parent class then it extends object class.

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Question 10

Ans) Option A ( It is directly accessible only in B1 )

Explanation:-

• Private variable can access the class itself.
• Here j is the class B1 variable,so it can access the j value.

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Question 11

Ans) Option E ( Z )

Explanation:-

• Private variable can access the class itself.
• Here z is the class B3 variable,so it can access the z value.

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Question 12

Ans) Option B( x,a,b )

Explanation:-

• Private variable can access the class itself and public or protected of parent class.
• Here a and b is in the classA2 variable and x is public variable of parent class A1, so it can access the x,a,b.

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Question 13

Ans) Option B( x,a,q )

Explanation:-

• Private variable can access the class itself and public or protected of parent class.
• Here x and a are in parent class public variables and q is its own variable, so it can access the x,a,q.

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Question 14

Ans) Option d (SOME_VALUE)

Explanation:-

• Static variables can access without instantiation of class object in java

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Question 15

ans) Option c (is-a relation)

Explanation:-

• In java inheritance is called "is-a" relation.