Question

Consider the following classes:

public class Clock extends Bear {
  public void method3()      {
    System.out.println("Clock 3");
  }
}

public class Lamp extends Can    {
  public void method1()      {
    System.out.println("Lamp 1");
  }

  public void method3()      {
    System.out.println("Lamp 3");
  }
}

public class Bear extends Can    {
  public void method1()      {
   System.out.println("Bear 1");
  }
  
  public void method3()      {
    System.out.println("Bear 3");
    super.method3();
  }
}

public class Can {
  public void method2()      {
    System.out.println("Can 2");
    method3();
  }

  public void method3()      {
    System.out.println("Can 3");
  }
}

---and that the following variables are defined:---

Object var1 = new Bear();
Can var2 = new Can();
Can var3 = new Lamp();
Bear var4 = new Clock();
Object var5 = new Can();
Can var6 = new Clock();

For each statement below , match the output produced in the right-hand column by the statement in the left-hand column. If the statement produces more than one line of output, the line breaks are indicated with slashes as in "a/b/c" to indicate three lines of output with "a" followed by "b" followed by "c". If the statement causes an error, choose in the right-hand column with either the phrase "compiler error" or "runtime error" to indicate when the error would be detected.

Note: Multiple statements can have the same output (ex: Compiler Error or Runtime Error)

var1.method2();

var2.method2();

var3.method2();

var4.method2();

var5.method2();

var1.method3();

var2.method3();

var3.method3();

var6.method3();

((Lamp)var6).method1();

((Can)var1).method1();

((Can)var1).method2();

((Bear)var1).method3();

((Clock)var1).method1();

---The choices for all methods are:---

Clock 3

Can 2/Can 3

Runtime Error

Compiler Error

Can 2/Bear 2/Can 3

Can 2/Clocl 3

Can 3

Bear3/Can 3

Answer 1

- Below is the code with the output.
- We need to add some cast to correct the compile time error
- There is a runtime error. I have added comments for the same
- Runtime Exception at line 30 of below image due to wrong reference as there is no method1 for clock class
- Compile time error at 3 places. added comments

Kindly upvote if this helped





CODE:

- Created a main class for testing the results.
- Output is in above image

package search;

public class DummyTest {
    public static void main(String[] args) {
        Object var1 = new Bear();
        Can var2 = new Can();
        Can var3 = new Lamp();
        Bear var4 = new Clock();
        Object var5 = new Can();
        Can var6 = new Clock();
        ((Can) var1).method2(); // compile time error - Add a cast here


        var2.method2();

        var3.method2();

        var4.method2();

        ((Can) var5).method2(); // compile time error - Add a cast here

        ((Bear) var1).method3(); // compile time error - Add a cast here

        var2.method3();

        var3.method3();

        var6.method3();

        ((Lamp) var6).method1(); // runtime error here due to wrong cast as method1 is in Lamp class . There is no method1 in clock class. as object is of class clock , so runtime error

        ((Bear) var1).method1(); // compile time error - change the cast here

        ((Can) var1).method2();

        ((Bear) var1).method3();

        ((Clock) var1).method1();
    }
}
class Clock extends Bear {
    public void method3() {
        System.out.println("Clock 3");
    }
}

class Lamp extends Can {
    public void method1() {
        System.out.println("Lamp 1");
    }

    public void method3() {
        System.out.println("Lamp 3");
    }
}

class Bear extends Can {
    public void method1() {
        System.out.println("Bear 1");
    }

    public void method3() {
        System.out.println("Bear 3");
        super.method3();
    }
}

class Can {
    public void method2() {
        System.out.println("Can 2");
        method3();
    }

    public void method3() {
        System.out.println("Can 3");
    }
}