Question 1

Which statement is true for the following code?

public class Plant {
   private String name;
   public Plant(String name) { this.name = name; }
   public String getName() { return name; }
}

public class Tree extends Plant {
   public void growFruit() { }
   public void dropLeaves() { }
}

java

The code will compile without changes.
The code will compile if public Tree() { Plant(); } is added to the Tree class.
The code will compile if public Plant() { Tree(); } is added to the Plant class.
The code will compile if public Plant() { this("fern"); } is added to the Plant class.

Answer

Correct Option: D

Question 2

What will the result for following code?

public class Yikes {
    public static void go(Long n) {System.out.println("Long ");}
    public static void go(Short n) {System.out.println("Short ");}
    public static void go(int n) {System.out.println("int ");}

    public static void main(String [] args) {
        short y = 6;
        long z = 7;
        go(y);
        go(z);
    }
}

java

int Long
Short Long
Compilation fails.
An exception is thrown at runtime.

Answer

Correct Option: A

Question 3

Which two statements are true about has-a and is-a relationships?

java

Inheritance represents an is-a relationship.
Inheritance represents a has-a relationship.
Interfaces must be used when creating a has-a relationship.
Instance variables can be used when creating a has-a relationship.

Answer

Correct Option: A,D

Question 4

Which two, independently, will allow Sub to compile?

1. class Super {
2.   private int a;
3.   protected Super(int a) { this.a = a; }
4. }
...
11. class Sub extends Super {
12.   public Sub(int a) { super(a); }
13.   public Sub() { this.a = 5; }
14. }

java

Change line 2 to: public int a;
Change line 2 to :protected int a;
Change line 13 to :public Sub() { this(5); }
Change line 13 to :public Sub() { super(5); }

Answer

Correct Option: C,D

Question 5

What will be the output?

public class Base {
  public static final String FOO = "foo";
  public static void main(String[] args) {
    Base b = new Base();
    Sub s = new Sub();
    System.out.print(Base.FOO);
    System.out.print(Sub.FOO);
    System.out.print(b.FOO);
    System.out.print(s.FOO);
    System.out.print(((Base)s).FOO);
  } 
}

class Sub extends Base {
    public static final String FOO="bar";
}

java

foofoofoofoofoo
foobarfoobarbar
foobarfoofoofoo
foobarfoobarfoo
barbarbarbarbar

Answer

Correct Option: D

Question 6

Which two statements are true?

java

An encapsulated, public class promotes re-use.
Classes that share the same interface are always tightly encapsulated.
An encapsulated class allows subclasses to overload methods, but does NOT allow overriding methods.
An encapsulated class allows a programmer to change an implementation without affecting outside code.

Answer

Correct Option: A,D

Question 7

What is the output?

public class Wow {
 public static void go(short n) {System.out.println("short");}
 public static void go(Short n) {System.out.println("SHORT");}
 public static void go(Long n) {System.out.println(" LONG");}
 public static void main(String [] args) {
   Short y = 6;
   int z = 7;
   go(y);
   go(z);
 }
}

java

short LONG
SHORT LONG
Compilation fails.
An exception is thrown at runtime.

Answer

Correct Option: C

Question 8

Which statement is true

public class CreditCard {

 private String cardID;
 private Integer limit;
 public String ownerName;

 public void setCardInformation(String cardID,
 String ownerName,
 Integer limit) {
  this.cardID = cardID;
  this.ownerName = ownerName;
  this.limit = limit;
 }
}

java

The class is fully encapsulated.
The code demonstrates polymorphism.
The ownerName variable breaks encapsulation.
The cardID and limit variables break polymorphism.
The setCardInformation method breaks encapsulation.

Answer

Correct Option: C

Question 9

What is the output?

interface TestA { String toString(); }
 public class Test {
 public static void main(String[] args) {
  System.out.println(new TestA() {
  public String toString() { return "test"; }
 });
 }
}

java

test
null
Compilation fails because of an error in line 1.
An exception is thrown at runtime.

Answer

Correct Option: A

Question 10

Which three methods, inserted individually at line 14, will correctly complete class Two?

class One {
 void foo() { }
}
class Two extends One {
 //insert method here
}

java

int foo() { /* more code here */ }
void foo() { /* more code here */ }
public void foo() { /* more code here */ }
private void foo() { /* more code here */ }
protected void foo() { /* more code here */ }

Answer

Correct Option: B,C,E

Description: Java OOPs Quiz - SCJP
Number of Questions: 10
Created by: Aliensbrain Bot
Tags: java scjp

Java OOPs Quiz - SCJP

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