Tag: java

Questions Related to java

A class cannot be declared:
java

  1. Static

  2. Private

  3. Default

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Correct Option: B

Following code will result in: int a = 3.5;
java

  1. Compilation error

  2. Runtime error

  3. a being 3.5

  4. a being 3.

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Correct Option: A
Explanation:

To solve this question, the user needs to have an understanding of variable types and type casting in programming.

Explanation for each option:

A. Compilation error: This option is correct. In many programming languages, including Java, assigning a floating-point value (such as 3.5) to an integer variable (such as int a) will result in a compilation error. This is because the two types are not compatible, and an explicit type casting is required.

B. Runtime error: This option is incorrect. Runtime errors occur when a program is executed and encounters an error, but in this case, the error would be caught by the compiler during the compilation phase.

C. a being 3.5: This option is incorrect. As mentioned earlier, assigning a floating-point value to an integer variable will result in a compilation error. The value 3.5 cannot be stored in an int variable.

D. a being 3: This option is incorrect. Since the value 3.5 cannot be stored in an int variable, the value of a will not be 3. The code will not compile, so no value will be assigned to a.

Therefore, the correct answer is:

A. Compilation error

Following code will result in: int a1 = 5; double a2 = (float)a1;
java

  1. Compilation error

  2. Runtime error

  3. No errors

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Correct Option: C
Explanation:

To solve this question, the user needs to understand the concept of type casting and data types in programming.

The given code snippet initializes an integer variable a1 with the value 5 and then assigns that value to a double variable a2 after performing a type casting to a float.

Now, let's go through each option and explain why it is right or wrong:

A. Compilation error: This option is incorrect. The code will compile without any errors because type casting from an integer to a float is allowed in most programming languages.

B. Runtime error: This option is incorrect. The code will not result in a runtime error because the type casting from an integer to a float is allowed and will not cause any issues at runtime.

C. No errors: This option is correct. The code will execute without any errors, and the value 5 will be successfully assigned to the a2 variable after the type casting.

Therefore, the correct answer is: C. No errors.

Following code will result in: int a = 9/0;
java

  1. Compilation error: Divisions must be in a try block.

  2. Compilation error: DivideByZeroException

  3. Runtime Exception

  4. No Error: a is NaN

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Correct Option: C

Following code will result in: float a = 9/0;
java

  1. Compilation error: Divisions must be in a try block

  2. Compilation error: DivideByZeroException

  3. Runtime Exception

  4. No Error: a is NaN

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Correct Option: C

A class can be transient
java

  1. True

  2. False

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Correct Option: B

Following code will result in: class A { int b = 1; public static void main(String [] args) { System.out.println("b is " + b); }}
java

  1. Compilation error

  2. Runtime Error

  3. Runtime Exception

  4. Output of b is 1

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Correct Option: A

Following code will result in: class A { public static void main(String [] args) {B b = new A(); }} class B extends A {}

java

  1. Compile error

  2. Runtime Exception

  3. No error

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Correct Option: A

AI Explanation

To answer this question, we need to understand the concept of inheritance and object creation in Java.

In the given code, we have two classes: A and B. Class A has a main method, which is the entry point of the program. Inside the main method, a new object b is created of type B using the constructor new A().

Now let's go through each option to understand why it is correct or incorrect:

Option A) Compile error - This option is correct. The code will result in a compile error because we are trying to create an object of type B using the constructor of class A. Since class B extends class A, it is valid to create an object of type B using the constructor of class B, but not vice versa. Therefore, the code B b = new A(); will result in a compile error.

Option B) Runtime Exception - This option is incorrect. There will be no runtime exception because the code will not compile in the first place.

Option C) No error - This option is incorrect. There will be a compile error, as explained in option A.

The correct answer is A) Compile error. This option is correct because we are trying to create an object of type B using the constructor of class A, which is not allowed in Java.

Following code will result in: class A { public static void main(String [] args) {A a = new B(); }} class B extends A {}
java

  1. Compiler error

  2. Runtime Exception

  3. No errors

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Correct Option: C

Methods that are marked protected can be called in any subclass of that class.

java

  1. True

  2. False

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Correct Option: A