Classes and Objects

Question 1

Scanner Class

Answer 1

Scanner is a class in java.util package used for obtaining the input of the primitive types like int, double etc. and strings. It is the easiest way to read input in a Java program, though not very efficient if you want an input method for scenarios where time is a constraint like in competitive programming.

Question 2

Package

Answer 2

A package is a namespace that organizes a set of related classes and interfaces. Conceptually you can think of packages as being similar to different folders on your computer.

Question 3

Steps in creating Scanner Class

Answer 3

Import:
import java.util.Scanner

Create Scanner:
Scanner input = new Scanner(System.in);

Prompt:
System.out.println(“Please enter your name:”)

Keyboard Input:
String firstName = input.next();

Question 4

Increment and Decrement Operators

Answer 4

Increment (++) and decrement (—) operators in Java programming let you easily add 1 to, or subtract 1 from, a variable.

Question 5

++var

i = 1
int j = ++i

Answer 5

Increment var by 1, and use the new var value in the statement

int j = ++1;
// j is 2 & i is 2

Question 6

var++

i = 1
int j = i++

Answer 6

Increment var by 1, and use the original var value in the statement

int j = 1++;
// j is 1 & i is 2

Question 7

–var

i = 1
int j = –i

Answer 7

Decrement var by 1, and use the new var value in the statement

int j = --1;
// j is 0 & i is 0

Question 8

var–

i = 1
int j = i–

Answer 8

Decrement var by 1, and use the original var value in the statement

int j = 1--;
// j is 1 & i is 0

Question 9

Type Casting

Answer 9

Type Casting in Java. Type casting is used to convert an object or variable of one type into another.

Question 10

Implicit Casting

Answer 10

An implicit cast means you don’t have to write code for the cast.

An implicit cast happens when you’re doing a widening conversion.

Question 11

Explicit Casting

Answer 11

An explicit casting is where you use some syntax to tell the program to do a conversion.

Question 12

Shorthand Assignment Operators

Answer 12

In addition to the basic assignment operator, Java also defines 12 shorthand assignment operators that combine assignment with the 5 arithmetic operators ( += , -= , *= , /= , %= ) and the 6 bitwise and shift operators ( &= , |= , ^= , «= ,&raquo_space;= ,&raquo_space;>= ).

Question 13

Comparison Operators

Answer 13

Operators
The result of every comparison is boolean (true or false).
operator 	meaning
<	less than
<=	less than or equal to
==	equal to
>=	greater than or equal to
>	greater than
!=	not equal