Getting Input From User

In this post, we are going to learn how to get input from the User. Then will do some programming exercises to enhance our programming knowledge.

There are Different - Different ways to get an input from the console -- Go HERE.
 but right now will stick to Scanner Class, because it is the most common and easiest way.

using Scanner Class will get the input from the user,

   

- The Scanner is a  class in java.

- present in java.util package

- which allows the user to read values of various types.

- There are far more methods in class Scanner than you will need in this course.

Syntax:- 

Scanner - is a class in java.

sc - is an object of Scanner class (you can give any name).

new - is an operator which is used to make an object of a class.

Scanner() - is a constructor in Scanner Class(Don't Worry will talk it later).

System - is a class in java, represents your computer system (helps to provide us system-level methods)

in - stands for input (s).

System.in - getting input from the system and it passes as an argument to Scanner Constructor.(Don't Worry, if you are unable to get it). 

# Scanner Class has Somes Methods to get Different kinds of values from the console.

- For different types of values different, types of methods are available.

- For int type nextInt() method is used,

- For double type nextDouble() method used,

- All the methods called by using Scanner Object (sc.method name).

- for example (String value) -- we have to use next() or nextLine().

String s; // variable -- where data store

Scanner sc = new Scanner(System,in); // creating Scanner class object 

s = sc.next(); // getting input from user and assgin it to "s" variable  

sc.close(); // good practic to close resourses.

Question -- WAP to Take two number from the user and return its sum.

Answer -- 

# Code 

package scannerClass;

import java.util.Scanner;

public class Sum {

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);
System.out.println("Enter 1st number : ");
int num1 =sc.nextInt();
System.out.println("Enter 2nd number : ");
int num2 = sc.nextInt();
int add=num1+num2;
System.out.println("Sum = "+add);
}
}

Control Statements (Part 3)

In this post will strictly discuss break and continue statement and then will see some of the programs that will help you to understand the concepts.


Break - 

+ Break statement (Keyword) in java. 

+ When the break statement is encountered inside a loop, the loop is immediately terminated and the program control resumes at the next statement following the loop.

+* It can be used to terminate a case in the switch statement.

Continue - 
+ The continue keyword can be used in any of the loop control structures. It causes the loop to immediately jump to the next iteration of the loop.
+ In a for loop, the continue keyword causes control to immediately jump to the update statement(Step).
+ In a while loop or do/while loop, control immediately jumps to the Boolean expression.

Let's See Some Programs based on this...



Ques 1: WAP (Write a program) to get a number user (1-7) and print its equivalent day.
(without break)

Explanation -  

User enter 5 in the console,
week = 5;
case 5 matches, after execution of case 5
all the rest case will execute because execution of program follows top to down approach.
that why you are getting
Thursday
Friday
Saturday
Invalid day  as an output



Ques 2: WAP (Write a program) to get a number user (1-7) and print its equivalent day.
(with break)

Explanation -  

User enter 5 in the console,
week = 5;
case 5 matches, after execution of case 5 (output is Thursday)
JVM encounter break statement,
all the rest case will not execute because execution of program follows top to down approach.
so after execution of case 5, break statement execute and break statements immediately terminated switch.



Ques 3: WAP (Write a program) to print number from 1 to 10. (Using for loop)

Will see three (3) cases --

 flow of execution of for loop Initialisation -> Condition check -> Loop body -> Iteration/Increment

Case 1: using for loop, printing 1 to 10.

Explanation -  

- for loop is used for counting.

- i =1 (counting start from 1)

- i<=10 (condition - till contidion setisfied, it will counting) 

- i++ increment (every time i=current value of i +1)

- output is 1 to 10.

Case 2:  using for loop, printing 1 to 10 ( with continue).

Explanation -  

- for loop is used for counting.

- i =1 (counting start from 1)

- i<=10 (condition - till condition satisfied, it will counting) 

- i++ increment (every time i=current value of i +1)

- there is an if condition,

• if condition true - control goes inside if block and continues execute, so when i=5  condition became true and continue statement executed then control goes for next iteration.
• if condition false - control never goes inside if block so the program will work as above case.

Case 3: using for loop, printing 1 to 10 ( with break).

Explanation -  

- for loop is used for counting.

- i =1 (counting start from 1)

- i<=10 (condition - till condition satisfied, it will counting) 

- i++ increment (every time i=current value of i +1)

- there is an if condition,

• if condition true - control goes inside if block and continues execute, so when i=5  condition became true and continue statement executed then control goes out of the loop.
• if condition false - control never goes inside if block so the program will work as above case.

Link to download these two programs... Click Here.



Now, In next post, I will tell you how to get INPUT From USER.
Using Scanner Class.

Control Statements (Part 2)

In this post, will talk about all Control Statements in details and Will see the syntax of it.
In next couple of part will see some of the examples that will definitely help you to understand better,
as well as I will going to give you some basics programming question to solve it.



Syntax - Syntax is the set of rules that defines the combinations of symbols that are considered to be a correctly structured document. (or in short, it is a grammar of programming)


Expression  - Expression is a valid and logical combination of the operator ( athematic and relational ) and number.


Boolean Expression - Boolean Expression is an expression which always gives its result either "true" or "false".




# if Statement

+ If the Boolean Expression / Condition gives true, then whatever written inside if block will execute.
+ If the Boolean Expression / Condition gives false, then whatever written inside if block will never execute.
+ Note - In the place of Boolean Expression / Condition, you can not use 0 or  1 (java is unlike C or C++).



# if else Statement 

+ If the Boolean Expression / Condition gives true, then whatever written in the place of "do this work 1" will execute.
+ If the Boolean Expression / Condition gives false, then whatever written in the place of "do this work 2" will never execute.
+ Note - In the place of Boolean Expression / Condition, you can not use 0 or  1 (java is unlike C or C++).



# switch Statement

+ The switch statement is also called Integer Based Decision Maker ( till Java 1.4).

+  X can be constant (final) and in the range.

+ in the place of X you can use Number (byte, short, integer), character, wrapper classes (will See later) and string (Sequence of characters).  

+ default is also a case if no case matches then default case will be executed. 

+*  in switch "break" and "continue", these two keywords will be used frequently. (will discuss in next post).

# while loop

+ it is also called Entry Controlled loop because it will check the condition before execution.
+ If the Boolean Expression / Condition gives true, then whatever written inside the block will execute repeatedly.
+ If the Boolean Expression / Condition return false, then whatever written inside the block will never execute and control goes out of the loop.
+ Note - In the place of Boolean Expression / Condition, you can not use 0 or  1 (java is unlike C or C++).



# do while loop

+ it is also called Exit Controlled loop because condition checks at the time of exit.
+ it will definitely going to be executed at once then checks for the condition.
+ If the Boolean Expression / Condition gives true, then whatever written inside the block will execute again.
+ If the Boolean Expression / Condition return false, then control goes out of the loop.
+ Note - In the place of Boolean Expression / Condition, you can not use 0 or  1 (java is unlike C or C++).



# for loop

+ it is used for counting purpose
+  it has three steps

• initialization - counting start from
• condition - do it, till the condition satisfied
• step - ascending to descending or descending to ascending

+ above steps are optional 

+ ; (semi-colon) is mandatory.

Control Statements (Part 1)

Control Statements are the statements which are used to make a group of statements and those groups of statements execute on some certain conditions. These are very useful while taking a decision on the basis of some boolean conditions.



In Java, control statements can be divided into the following three categories:

♣  Sequential Statement (Liner Statement)
♣  Selection Statements (Branching)
♣  Iteration Statements (Loop)

# Sequential Statement (Liner Statement) 

In a program, all statements execute one by one.
Staring from 1st statement to till the last statement.
This is called Sequential Statements.

For Example:-

  

# Selection Statements (Branching)

In Selection/Branching, you just make a group of some similar kinds of statement that together performs some specific kind of job.
We use if, if else to make the group of statements.
It is very useful for decision making on the basis of right or wrong  / true false.

For Example:- if, if else, switch

# Iteration Statements (Loop)

these are some group of statements that executed rapidly till a certain condition is not satisfied.
There are only three kinds of looping/iterative statements till now.
1-for loop
2-while loop (Entry Control loop)
3-do while loop (Exit Control loop)