Methods in Java tutorial and Interview Questions and Answers

Methods in Java

Study and learn Interview MCQ Questions and Answers on Methods in Java . Attend job interviews easily with these Multiple Choice Questions

Methods in Java

Java Method Signature is nothing but a combination of Return-Type, Method’s Name and a Parameter list it accepts.

The method signature or syntax is as follows.

type METHODNAME(type param1, type param2..)
{
  //statements
  //..
  //return statement
}

Let us know about parts of Java Method Signature.

  1. Return Type
  2. Method Name
  3. Parameter List

1. Return Type: A Java method may or may not return a value. If it returns nothing, we specify it explicitly mentioning a “void” before it. A method can return pri-mitive or Object type values.

2. Method Name: A Java Method Name can be a combination of Alphabets, Numbers and Special Symbols (Underscore and Dollar only).

Methods in Java Naming Rules:

  • Method name can start with a Letter or Alphabet.
  • Method name can start with either Underscore(_) or Dollar($) symbol.
  • and Method name can not start with a number.
  • Method name can contain numbers in-between or at the end.
  • and Method name can not be a keyword.

3. Parameter List: Java methods can contain any number of parameters of any type. There can be zero parameters also. Variables which are part of a Parameter-list are also called Local Variables. Local variables are stored in Stack Memory. Also, the variables declared inside a method are also called Local Variables or Method Variables.

Naming Conventions or Rules for Local Variables:

  • Name of a Local variable can start with an Alphabet lowercase or uppercase. Lowercase is preferred.
  • Name of a Local variable can start with either an Underscore(_) or Dollar($) symbol.
  • and Name of a Local variable can not start with a number but it can contain numbers in-between or at the end.
  • Name can not be a keyword.
  • No two Local variables should have the same name.

An example Java program below explains how to pass arguments to a Java method and return values or objects from a method.

class Table
{
  int height;
}

public class JavaMethodExample
{	
  public static void main(String[] args)
  {
    JavaMethodExample je = new JavaMethodExample();
    Table t1 = new Table();
    t1.height = 10;
    je.show(t1); //Passing arguments to method

    int changedValue = je.increase(t1);
    System.out.println("New Height= " + changedValue);
    //System.out.println("New Height= " + t1.height); //This code also works
  }

  void show(Table tab) //Receiving parameters in method
  {
    System.out.println("Height= " + tab.height);
  }

  int increase(Table tab) //Returning a value
  {
    tab.height = tab.height + 20;
    return tab.height;
  }	

}
//OUTPUT
//Height= 10
//New Height= 30

Note

In the above example, the method “show” receives parameters. The method “increase” receives an object reference as a parameter and returns an integer value back to the calling method. Remember that “main” is also a method which is the starting point of program execution.

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[WpProQuiz 158]

Methods in Java MCQ (Interview)

1) A Java method is comparable to a __ in c language.

A) structure

B) union

C) function

D) enum

Answer [=] C

2) All Java methods must have a return type. (TRUE / FALSE)

A) TRUE

B) FALSE

Answer [=] A

3) State TRUE or FALSE. A Java method can have the same name as the class name.

A) TRUE

B) FALSE

Answer [=] A

4) In Java, add a ___ to a constructor to convert it into a method.

A) if statement

B) static

C) return type

D) semicolon

Answer [=] C

5) Java method signature is a combination of ___.

A) Return type

B) Method name

C) Argument List

D) All the above

Answer [=] D

6) In Java, a method name can not start with a ___.

A) number

B) # (pound)

C) – (hyphen)

D) All the above

Answer [=] D

7) In Java, a method name can start with ___.

A) Alphabet

B) Underscore (_)

C) Dollar ($)

D) All the above

Answer [=] D

8) In Java, a method name can contain numbers from 2nd character onwards. (TRUE / FALSE).

A) TRUE

B) FALSE

Answer [=] A

9) Choose the correct identifier for a method name in Java.

A) 1show

B) $hide

C) *show$

D) 3_click

Answer [=] B

10) What is the output of the below Java program with an empty return statement?

public class TestingMethods2
{
  void show()
  {
    System.out.println("SHOW Method..");
    return;
  }
  public static void main(String[] args)
  {
    TestingMethods2 t2 = new TestingMethods2();
    t2.show();
  }
}

A) SHOW Method..

B) No output

C) Compiler error

D) None

Answer [=] A

Explanation:

Yes. A void method can use an empty return statement.

11) What is the output of the below Java program with a void method?

public class TestingMethods3
{
  void show2()
  {
    System.out.println("SHOW Method 2");
  }
  public static void main(String[] args)
  {
    TestingMethods3 t3 = new TestingMethods3();
    t3.show2();
  }
}

A) SHOW Method 2

B) No output

C) Compiler error

D) None

Answer [=] A

Explanation:

The empty return statement is not necessary for a void method.

12) A “this” operator used inside a Java method refers to ___ variable.

A) Global variable

B) Method local variable

C) Instance variable

D) None

Answer [=] C

13) What is the output of the below Java program with a “this” operator?

public class TestingMethods4
{
  int cakes=5;
  void order(int cakes)
  {
    this.cakes = cakes;
  }
  public static void main(String[] args)
  {
    TestingMethods4 t4 = new TestingMethods4();
    t4.order(10);
    System.out.println("CAKES=" + t4.cakes);
  }
}

A) CAKES=5

B) CAKES=0

C) CAKES=10

D) Compiler error

Answer [=] C

Explanation:

In the program, this.cakes refers to the instance variable cakes.

14) A local variable declared inside a method can not be used in expressions without initializing it first. (TRUE / FALSE).

A) TRUE

B) FALSE

Answer [=] A

15) What is the output of the below Java program?

public class TestingMethods5
{
  public static void main(String[] args)
  {
    int localVariable;
    System.out.println(localVariable);
  }
}

A) 0

B) garbage value

C) NullPointerException

D) Compiler error

Answer [=] D

Explanation:

In the above program, the localVariable is a Local variable and it is not initialized. You can not use it in any expressions, not even printing.

16) In Java, local variables are stored in __ memory and instance variables are stored in ___ memory.

A) Stack, Stack

B) Heap, Heap

C) Stack, Heap

D) Heap, Stack

Answer [=] C

17) A static-method or a static-variable is shared among all instances of a class. (TRUE / FALSE)

A) TRUE

B) FALSE

Answer [=] A

Explanation:

Yes. a single copy of a static variable or method is common to all instance objects.

18) What is the output of the Java program with static variables?

public class TestingMethods6
{
  static int cats=25;
  public static void main(String[] args)
  {
    TestingMethods6 t6 = new TestingMethods6();
    System.out.println("t6 BIRDS before=" + t6.cats);
    TestingMethods6 t7 = new TestingMethods6();
    t7.cats = 10;
    System.out.println("t6 BIRDS after=" + t6.cats);
  }
}

A)

t6 BIRDS before=25
t6 BIRDS after=25

B)

t6 BIRDS before=25
t6 BIRDS after=10

C)

t6 BIRDS before=25
t6 BIRDS after=0

D) None

Answer [=] B

Explanation:

The static variable “cats” is common to all objects. There is no separate copy like non-static variables.

19) What is the output of the below Java program with a final local variable?

public class TestingMethods8
{
  int cars = 20;
  void change(final int cars)
  {
    cars = 10;
    this.cars = cars;
  }
  public static void main(String[] args)
  {
    TestingMethods8 t8 = new TestingMethods8();
    t8.change(30);
    System.out.println(t8.cars);
  }
}

A) 30

B) 20

C) 10

D) Compiler error

Answer [=] D

Explanation:

The argument that is marked final can not be reassigned or changed. So, the compiler error is produced. So, the statement cars=10; inside the change() method is wrong.

20) Java does not allow nesting of methods. (TRUE / FALSE)

A) TRUE

B) FALSE

Answer [=] A

21) What is the output of the below Java program?

class Road
{
  static void show()
  {
    System.out.println("Inside static method.");
  }
}

public class TestingMethods10
{
  public static void main(String[] args)
  {
    Road.show();
  }
}

A) Inside static method.

B) empty message

C) Compiler error

D) Runtime error / exception

Answer [=] A

Explanation:

You can directly call static methods of a class with just a DOT operator and class-name.

22) What is the output of the below Java program?

class SomeClass
{
  char batch = 'A';
}

public class TestingMethods11
{
  public static void main(String[] args)
  {
    SomeClass a1 = new SomeClass();
    System.out.println("Before: " + a1.batch);
    SomeClass a2 = new SomeClass();
    a2.batch = 'B';
    System.out.println("After: " + a1.batch);
  }
}

A)

Before: A
After: B

B)

Before: A
After: A

C)

Before: A
After:

D)

Before: B
After: B

Answer [=] B

Explanation:

Instance variable “batch” is separate for each instance. So the changes to one instance object does not affect another instance object.


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