Basic Questions

Question 1

Is Java platform independent?

Answer 1

Yes. We can write java code on one platform and run it on another platform.

Question 2

Explain public static void main(String args[])

Answer 2

Here public is an access modifier, which means that this method is accessible by any class.

static – static keyword tells that this method can be accessed without creating the instance of the class. Refer: Static keyword in java

void – this main method returns no value.

main – It is the name of the method.

String args[] – The args is an array of String type. This contains the command line arguments that we can pass while running the program.

Question 3

What is javac ?

Answer 3

javac produces the java byte code from the source code written *.java file. JVM executes the bytecode to run the program.

Question 4

What is class?

Answer 4

A class is a blueprint or template or prototype from which you can create the object of that class. A class has set of properties and methods that are common to its objects.

Question 5

What is the base class of all classes?

Answer 5

java.lang.Object is the base class (super class) of all classes in java.

Question 6

What is a wrapper class in Java?

Answer 6

A wrapper class converts the primitive data type such as int, byte, char, boolean etc. to the objects of their respective classes such as Integer, Byte, Character, Boolean etc

Question 7

What is a path and classPath in Java?

Answer 7

Path specifies the location of .exe files. Classpath specifies the location of bytecode (.class files).

Question 8

Different Data types in Java

Answer 8

byte – 8 bit
short – 16 bit
char – 16 bit Unicode
int – 32 bit (whole number)
float – 32 bit (real number)
long – 64 bit (Single precision)
double – 64 bit (double precision)

Question 9

What is Unicode?

Answer 9

Java uses Unicode to represent the characters. Unicode defines a fully international character set that can represent all of the characters found in human languages.

Question 10

What are Literals?

Answer 10

Any constant value that is assigned to a variable is called literal in Java

Question 11

What is an Array?

Answer 11

An array is a collection (group) of fixed number of items. Array is a homogeneous data structure which means we can store multiple values of same type in an array but it can’t contain multiple values of different types. For example an array of int type can only hold integer values.

Question 12

What is BREAK statement in java?

Answer 12

The break statement is used to break the flow sequence in Java.

break statement is generally used with switch case data structure to come out of the statement once a case is executed.
It can be used to come out of the loop in Java

Question 13

byte

Answer 13

8 bit integer

Question 14

short

Answer 14

16 bit integer

Question 15

char

Answer 15

16 bit unicode

Question 16

int

Answer 16

32 bit integer

Question 17

float

Answer 17

32 bit real number

Question 18

long

Answer 18

64 bit integer

Question 19

double

Answer 19

64 bit real number

Question 20

boolean

Answer 20

true/false