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Q1. Class StaticField {
static int i = 7;
public static void main(String[] args) {
StaticFied obj = new StaticField();
obj.i++;
StaticField.i++;
obj.i++;
System.out.println(StaticField.i + " "+ obj.i);
}
}
What is the result?
A. 10 10
B. 8 9
C. 9 8
D. 7 10
Answer: A
Q2. Given:
And the commands:
Javac Test.java
Java Test 12345
What is the result?
A. Number us : 12345
B. A NullPointerException is thrown at runtime
C. A NumberFormatException is thrown at runtime
D. AnArrayIndexOutOfBoundException is thrown at runtime.
Answer: A
Q3. Given the following main method:
What is the result?
A. 5 4 3 2 1 0
B. 5 4 3 2 1
C. 4 2 1
D. 5
E. Nothing is printed
Answer: D
Explanation:
Loop will run only once and after that num == 0 will break it After first cycle of the loop.
Q4. Which three statements are true about the structure of a Java class?
A. A class can have only one private constructor.
B. A method can have the same name as a field.
C. A class can have overloaded static methods.
D. A public class must have a main method.
E. The methods are mandatory components of a class.
F. The fields need not be initialized before use.
Answer: A,B,C
Explanation: A: Private constructors prevent a class from being explicitly instantiated by its
callers.
If the programmer does not provide a constructor for a class, then the system will always
provide a default, public no-argument constructor. To disable this default constructor,
simply add a private no-argument constructor to the class. This private constructor may be
empty.
B: The following works fine:
int cake() {
int cake=0;
return (1);
}
C: We can overload static method in Java. In terms of method overloading static method
are just like normal methods and in order to overload static method you need to provide
another static method with same name but different method signature.
Incorrect:
Not D: Only a public class in an application need to have a main method.
Not E:
Example:
class A
{
public string something;
public int a;
}
Q: What do you call classes without methods? Most of the time: An anti pattern.
Why? Because it faciliates procedural programming with "Operator" classes and data
structures. You separate data and behaviour which isn't exactly good OOP.
Often times: A DTO (Data Transfer Object)
Read only datastructures meant to exchange data, derived from a business/domain object.
Sometimes: Just data structure.
Well sometimes, you just gotta have those structures to hold data that is just plain and
simple and has no operations on it.
Not F: Fields need to be initialtized. If not the code will not compile.
Example:
Uncompilable source code - variable x might not have been initialized
Q5. Given:
public class TestLoop {
public static void main(String[] args) {
int array[] = {0, 1, 2, 3, 4};
int key = 3;
for (int pos = 0; pos < array.length; ++pos) {
if (array[pos] == key) {
break;
}
}
System.out.print("Found " + key + "at " + pos);
}
}
What is the result?
A. Found 3 at 2
B. Found 3 at 3
C. Compilation fails
D. An exception is thrown at runtime
Answer: C
Explanation: The following line does not compile: System.out.print("Found " + key + "at " + pos);
The variable pos is undefined at this line, as its scope is only valid in the for loop. Any variables created inside of a loop are LOCAL TO THE LOOP.
Q6. Given the following class:
And given the following main method, located in another class:
Which three lines, when inserted independently at line n1, cause the program to print a o balance?
A. this.amount = 0;
B. amount = 0;
C. acct (0) ;
D. acct.amount = 0;
E. acct. getAmount () = 0;
F. acct.changeAmount(0);
G. acct.changeAmount(-acct.amount);
H. acct.changeAmount(-acct.getAmount());
Answer: D,G,H
Q7. Given the code fragment:
What is the result?
A. Values are : [EE, ME]
B. Values are : [EE, EE, ME]
C. Values are : [EE, ME, EE]
D. Values are : [SE, EE, ME, EE]
E. Values are : [EE, ME, SE, EE]
Answer: E
Q8. A method is declared to take three arguments. A program calls this method and passes only two arguments. What is the results?
A. Compilation fails.
B. The third argument is given the value null.
C. The third argument is given the value void.
D. The third argument is given the value zero.
E. The third argument is given the appropriate falsy value for its declared type. F) An
exception occurs when the method attempts to access the third argument.
Answer: A
Q9. Given the following four Java file definitions:
// Foo.java
package facades;
public interface Foo { }
// Boo.java
package facades;
public interface Boo extends Foo { }
// Woofy.java
package org.domain
// line n1
public class Woofy implements Boo, Foo { }
// Test.java
package.org;
public class Test {
public static void main(String[] args) {
Foo obj=new Woofy();
Which set modifications enable the code to compile and run?
A. At line n1, Insert: import facades;At line n2, insert:import facades;import org.domain;
B. At line n1, Insert: import facades.*;At line n2, insert:import facades;import org.*;
C. At line n1, Insert: import facades.*;At line n2, insert:import facades.Boo;import org.*;
D. At line n1, Insert: import facades.Foo, Boo;At line n2, insert:import org.domain.Woofy;
E. At line n1, Insert: import facades.*;At line n2, insert:import facades;import org.domain.Woofy;
Answer: E
Q10. Given the code in a file Traveler.java:
And the commands:
Javac Traveler.java
Java Traveler Java Duke What is the result?
A. Happy Journey! Duke
B. Happy Journey! Java
C. An exception is thrown at runtime
D. The program fails to execute due to a runtime error
Answer: D
Q11. Given the code fragment:
Which two modifications, when made independently, enable the code to print joe:true: 100.0?
A. Option A
B. Option B
C. Option C
D. Option D
E. Option E
Answer: A,C
Q12. Given:
What will be the output?
A. Option A
B. Option B
C. Option C
D. Option D
Answer: D
Q13. Given:
public class Test {
public static void main(String[] args) {
int ax = 10, az = 30;
int aw = 1, ay = 1;
try {
aw = ax % 2;
ay = az / aw;
} catch (ArithmeticException e1) {
System.out.println("Invalid Divisor");
} catch (Exception e2) {
aw = 1;
System.out.println("Divisor Changed");
}
ay = az /aw; // Line 14
System.out.println("Succesful Division " + ay);
}
}
What is the result?
A. Invalid Divisor
Divisor Changed
Successful Division 30
B. Invalid Divisor
Successful Division 30
C. Invalid Divisor
Exception in thread "main" java.lang.ArithmeticException: / by zero
at test.Teagle.main(Teagle.java:14)
D. Invalid Divisor
Exception in thread "main" java.lang.ArithmeticException: / by zero
at test.Teagle.main(Teagle.java:14)
Successful Division 1
Answer: C
Q14. Given the code fragment:
Which statement is true?
A. After line 8, three objects are eligible for garbage collection
B. After line 8, two objects are eligible for garbage collection
C. After line 8, one object is eligible for garbage collection
D. After line 8, none of the objects are eligible for garbage collection
Answer: C
Q15. Consider following method
Which statement is true?
A. This method is invalid.
B. This method can be used only in an interface.
C. This method can return anything.
D. This method can be used only in an interface or an abstract class.
E. None of above.
Answer: B
Explanation:
Given method is declared as default method so we can use it only inside an interface.
Hence option B is correct and option D is incorrect.
Option A is incorrect as it is valid method. Option C is incorrect as return type is void, which
means we can't return anything.