The Java conditionals structures & loops

1 - Conditional structure If & else else in Java

In Java, an if statement is a conditional statement that executes a set of statements according to a condition whether it is verified or not.

Syntax:

 if( condition ){
set
of
statements
......
}
else{
set
of
statement...
...
}

Example

int youAge=19;
if(yourAge <= 18 ){
System.out.println("You are minor, because your age is : " + yourAge );
}
else{
System.out.println("You are major, because your age is : " + yourAge );
}

Here is a complete example

Example

import java.util.Scanner;

public class If {


    public static void main(String[] args) {

    System.out.println("How old are you !");

    Scanner age=new Scanner(System.in);

    int yourAge=age.nextInt();

    if ( yourAge < 18 ) {

System.out.println("you are minor, because your age is : "+ yourAge);

    }

    else{

        System.out.println("you are majorr, because your age is : "+ yourAge);   

    }

    age.close();

}

}

This displays:

You are major, if the age typed is> = 18
You are minor, if the age typed is <18

Note :

The else {  command is not required

2 - Loop For Java

There are many situations that require you to run a block of instructions several times in  your applications. Loops can execute a block of code a number of times. The for Java loop  will be useful in this case

Syntax:

For (start counter, end counter, counter increment) {

Block of instructions

}

Example:

For (int i = 1; i <= 10; i ++) {

System.out.println ("hello!");

}

The above example shows 10 times the message "Hello !"

Hello !
Hello !
Hello !
Hello !
Hello !
Hello !
Hello !
Hello !
Hello !
Hello !

3 - Java while loop

The while loop is a control statement that allows the code to be repeatedly executed as long as a boolean condition is achieved.

Syntax:

While (condition) {


Block of instructions ...

}

Example

Int i = 1;

While (i <= 10) {

System.out.println ("hello!");

i ++;

}

The above example shows 10 times the message hello! And stops.