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- Question
What will be the output of the program?
public class Test { public static void main(String [] args) { int I = 1; do while ( I < 1 ) System.out.print("I is " + I); while ( I > 1 ) ; } }
Options- A. I is 1
- B. I is 1 I is 1
- C. No output is produced.
- D. Compilation error
- Correct Answer
- No output is produced.
ExplanationThere are two different looping constructs in this problem. The first is a do-while loop and the second is a while loop, nested inside the do-while. The body of the do-while is only a single statement-brackets are not needed. You are assured that the while expression will be evaluated at least once, followed by an evaluation of the do-while expression. Both expressions are false and no output is produced.
More questions
- 1. What will be the output of the program?
String x = "xyz"; x.toUpperCase(); /* Line 2 */ String y = x.replace('Y', 'y'); y = y + "abc"; System.out.println(y);
Options- A. abcXyZ
- B. abcxyz
- C. xyzabc
- D. XyZabc Discuss
Correct Answer: xyzabc
Explanation:
Line 2 creates a new String object with the value "XYZ", but this new object is immediately lost because there is no reference to it. Line 3 creates a new String object referenced by y. This new String object has the value "xyz" because there was no "Y" in the String object referred to by x. Line 4 creates a new String object, appends "abc" to the value "xyz", and refers y to the result.- 2. What will be the output of the program?
public class SwitchTest { public static void main(String[] args) { System.out.println("value =" + switchIt(4)); } public static int switchIt(int x) { int j = 1; switch (x) { case l: j++; case 2: j++; case 3: j++; case 4: j++; case 5: j++; default: j++; } return j + x; } }
Options- A. value = 2
- B. value = 4
- C. value = 6
- D. value = 8 Discuss
Correct Answer: value = 8
Explanation:
Because there are no break statements, once the desired result is found, the program continues though each of the remaining options.- 3. What will be the output of the program?
public class If2 { static boolean b1, b2; public static void main(String [] args) { int x = 0; if ( !b1 ) /* Line 7 */ { if ( !b2 ) /* Line 9 */ { b1 = true; x++; if ( 5 > 6 ) { x++; } if ( !b1 ) x = x + 10; else if ( b2 = true ) /* Line 19 */ x = x + 100; else if ( b1 | b2 ) /* Line 21 */ x = x + 1000; } } System.out.println(x); } }
Options- A. 0
- B. 1
- C. 101
- D. 111 Discuss
Correct Answer: 101
Explanation:
As instance variables, b1 and b2 are initialized to false. The if tests on lines 7 and 9 are successful so b1 is set to true and x is incremented. The next if test to succeed is on line 19 (note that the code is not testing to see if b2 is true, it is setting b2 to be true). Since line 19 was successful, subsequent else-if's (line 21) will be skipped.- 4. What will be the output of the program?
public class A { void A() /* Line 3 */ { System.out.println("Class A"); } public static void main(String[] args) { new A(); } }
Options- A. Class A
- B. Compilation fails.
- C. An exception is thrown at line 3.
- D. The code executes with no output. Discuss
Correct Answer: The code executes with no output.
Explanation:
Option D is correct. The specification at line 3 is for a method and not a constructor and this method is never called therefore there is no output. The constructor that is called is the default constructor.- 5. What will be the output of the program?
class Test { public static void main(String [] args) { Test p = new Test(); p.start(); } void start() { boolean b1 = false; boolean b2 = fix(b1); System.out.println(b1 + " " + b2); } boolean fix(boolean b1) { b1 = true; return b1; } }
Options- A. true true
- B. false true
- C. true false
- D. false false Discuss
Correct Answer: false true
Explanation:
The boolean b1 in the fix() method is a different boolean than the b1 in the start() method. The b1 in the start() method is not updated by the fix() method.- 6. What will be the output of the program?
class Test { static int s; public static void main(String [] args) { Test p = new Test(); p.start(); System.out.println(s); } void start() { int x = 7; twice(x); System.out.print(x + " "); } void twice(int x) { x = x*2; s = x; } }
Options- A. 7 7
- B. 7 14
- C. 14 0
- D. 14 14 Discuss
Correct Answer: 7 14
Explanation:
The int x in the twice() method is not the same int x as in the start() method. Start()'s x is not affected by the twice() method. The instance variable s is updated by twice()'s x, which is 14.- 7. You want a class to have access to members of another class in the same package. Which is the most restrictive access that accomplishes this objective?
Options- A. public
- B. private
- C. protected
- D. default access Discuss
Correct Answer: default access
Explanation:
The only two real contenders are C and D. Protected access Option C makes a member accessible only to classes in the same package or subclass of the class. While default access Option D makes a member accessible only to classes in the same package.- 8. What will be the output of the program?
class Super { public int i = 0; public Super(String text) /* Line 4 */ { i = 1; } } class Sub extends Super { public Sub(String text) { i = 2; } public static void main(String args[]) { Sub sub = new Sub("Hello"); System.out.println(sub.i); } }
Options- A. 0
- B. 1
- C. 2
- D. Compilation fails. Discuss
Correct Answer: Compilation fails.
Explanation:
A default no-args constructor is not created because there is a constructor supplied that has an argument, line 4. Therefore the sub-class constructor must explicitly make a call to the super class constructor:- 9. 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
Programming
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- 1. What will be the output of the program?