Core Java - Interview Questions and Answers for 'Variable' | Search Interview Question

Interview Questions and Answers - Order By Rating

Q31. What are the disadvantages of using arrays ?

Ans. Arrays are of fixed size and have to reserve memory prior to use. Hence if we don't know size in advance arrays are not recommended to use.

Arrays can store only homogeneous elements.

Arrays store its values in contentious memory location. Not suitable if the content is too large and needs to be distributed in memory.

There is no underlying data structure for arrays and no ready made method support for arrays, for every requriment we need to code explicitly

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Q32. Are there any global variables in Java, which can be accessed by other part of your program?

Ans. No. Global variables are not allowed as it wont fit good with the concept of encapsulation.

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Advanced level question usually asked to senior developers , leads and architects.

Q33. How does volatile affect code optimization by compiler?

Core Java

Ans. Volatile is an instruction that the variables can be accessed by multiple threads and hence shouldn't be cached. As volatile variables are never cached and hence their retrieval cannot be optimized.

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Q34. What data type Variable can be used in a switch statement ?

Core Java

Ans. Variables used in a switch statement can only be a byte, short, int, or char ( and String with Java 7 and above )

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Q35. What environment variables do I need to set on my machine in order to be able to run Java programs?

Ans. CLASSPATH and PATH are the two variables.

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Q36. Will the static block be executed in the following code ? Why ?

class Test
{
static
{
System.out.println("Why I am not executing ");
}
public static final int param=20;
}

public class Demo
{
public static void main(String[] args)
{
System.out.println(Test.param);
}
}

Ans. No the static block won't get executed as the referenced variable in the Test class is final. Compiler replaces the content of the final variable within Demo.main method and hence actually no reference to Test class is made.

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Q37. Will static block for Test Class execute in the following code ?

class Test
{
static
{
System.out.println("Executing Static Block.");
}
public final int param=20;

public int getParam(){
return param;
}
}

public class Demo
{
public static void main(String[] args)
{
System.out.println(new Test().param);
}
}

Ans. Yes.

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Q38. What do you mean by "Java is a statically typed language" ?

Core Java

Ans. It means that the type of variables are checked at compile time in Java.The main advantage here is that all kinds of checking can be done by the compiler and hence will reduce bugs.

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Q39. What are the conventions regarding constant variables or static final variables ?

Core Java

Ans. They should be named all in upper case with underscore separating words.

Moreover the name should be such that it identifies the value. For example, if we are using constant for employee Id 123, it should be named something like EMPLOYEE_ID_123 and not EMPLOYEE_ID

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Q40. Why is a constant defined as a static final in Java?

Core Java

Ans. Final makes sure that the value doesn't change after initialization and static makes sure that there is only one copy that can be shared across objects.

Making it non static will unnecessarily create a different copy per object wherein the same value will kept for all copies ( as its final and cannot be changed ).

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Q41. What are the advantages and disadvantages of static variables and static methods ?

Core Java

Ans. Advantages

Can do meta object operations ( like validating something before creating objects , keep count of number of objects )

Can do operations which have nothing to do with objects but still you want them to be tied to Class.

Disadvantages

Commonly used to static variables sometime leads to problems due to access by different objects.

Are not tied to objects so doesn't reflect pure Object Oriented approach.

Needs to be synchronized so as to avoid update conflicts by mutiple objects and threads.

Some limitation in testing as not all frameworks have facility to mock them. Powermock has but Mockito doesnt

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Q42. Variables of an interface are intrinsically ...

a. transient
b. final
c. public
d. static

Ans. b,c and d i.e final , public and static

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Q43. Which of the following is not true for final variables ?

a. They cannot be changed after initialization
b. They can be initialized within static method
c. They can be declared and initialized together at the same place
d. They can be initialized within constructor

Ans. They can be initialized within static method

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Q44. What is an instance variable?

a. An instance or object of an class
b. The field of an object
c. Any variable of a class
d. None of the above

Ans. The field of an object

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