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- Question
Which two of the following statements, inserted independently, could legally be inserted into missing section of this code?
- boolean test = (Component instanceof t);
- boolean test = (t instanceof Ticker);
- boolean test = t.instanceof(Ticker);
- boolean test = (t instanceof Component);
import java.awt.*; class Ticker extends Component { public static void main (String [] args) { Ticker t = new Ticker(); /* Missing Statements? */ } }
Options- A. 1 and 4
- B. 2 and 3
- C. 1 and 3
- D. 2 and 4
- Correct Answer
- 2 and 4
Explanation(2) is correct because class type Ticker is part of the class hierarchy of t; therefore it is a legal use of the instanceof operator. (4) is also correct because Component is part of the hierarchy of t, because Ticker extends Component.(1) is incorrect because the syntax is wrong. A variable (or null) always appears before the instanceof operator, and a type appears after it. (3) is incorrect because the statement is used as a method (t.instanceof(Ticker);), which is illegal.
More questions
- 1. What will be the output of the program (in jdk1.6 or above)?
public class BoolTest { public static void main(String [] args) { Boolean b1 = new Boolean("false"); boolean b2; b2 = b1.booleanValue(); if (!b2) { b2 = true; System.out.print("x "); } if (b1 & b2) /* Line 13 */ { System.out.print("y "); } System.out.println("z"); } }
Options- A. z
- B. x z
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- 1. What will be the output of the program (in jdk1.6 or above)?