1D Array Revision by java

Abdelrhman khaled — Wed, 12 Apr 2023 08:51:22 +0000

Quickly, we will recap about 1D array and do some iterations on it

Declaration

DataType nameOfArray [] = new DataType [lengthOfArray];

Example
int array [] = new int [5];

If I want to access an element in array

ArrayName[index]

array[2];

Note that arrays is zero based:

Array of length 5
The 1st element in array[0]
The last element array[lengthOfArray-1] = array[4]

Example

int array [] = new int [5];
array [0] = 7;
array [1] = 23;
array [2] = 20;
array [3] = 17;
array [4] = 45;

System.out.println( array[0] ); // will print 7

looping on 1D array

For (int i=0 ; i<array.length();i++)
{
System.out.println(array[i] ) ;
}

Great questions need some one to solve

1st and easy question

2nd question and easy too

last one but is medium !

Java HackerRank AUFS Season 6

Abdelrhman khaled — Mon, 06 Mar 2023 12:43:17 +0000

What we toke in session 2

1- how to print a sentence
System.out.print("hello in HackerRank");
or
System.out.println("hello in HackerRank with");

special characters needed to print

\\ will print \
\' will print '
\" will print "
\n will make a new line
\t will make a horizontal tab

let's print that sentence

hello\Abdelrhman\2002\new Year

System.out.println("hello\\Abdelrhman\\2002\\new year");

take care if you want to print \ or another special characters, to print it in the form\\.

2- naming identifiers
an identifier (a variable name) can be a sequence of Unicode characters that represent letters, digits 0-9, a dollar sign ($), or an underscore (_).

some limitations

The first symbol of an identifier cannot be a digit.
An identifier cannot have the same spelling as a keyword.
It cannot be spelled as the boolean literal true or false, and or as the literal null.
an identifier cannot be just an underscore (_).

Here are a few unusual but legal examples of identifiers:
$$
_30
String
ατηρε

3- Data Types
here is some data types we have in java

Boolean
to store true or false
short
int
long
to store Integer numbers
float
double
to store Decimal numbers like 3.31
char
to store a single character
Stirng
to store a text

that's good but what is the difference between short, int, long ?
Is the maximum and minimum value that can hold .

So let's see what is the maximum and minimum value that short dataType can hold

System.out.println(Short.MAX_VALUE);
System.out.println(Short.MIN_VALUE);

that will print
32767
-32768

so if you try to store a value like 999999 in a short variable it will give an error.

try to know maximum and minimum value that int and long can hold

System.out.println(Integer.MAX_VALUE);
System.out.println(Integer.MIN_VALUE);

System.out.println(Long.MAX_VALUE);
System.out.println(Long.MIN_VALUE);

NOW let's assign a value to a variable

int age = 21;
String name = "Abdelrhman Khaled";
System.out.println("My name is: "+name +" And my age is: "+age);

4- some usefull functions in class Integer

Let's try to convert numbers from int to Binary and Octal...

System.out.println(Integer.toBinaryString(42));
System.out.println(Integer.toOctalString(42));
System.out.println(Integer.toHexString(42));

That is very great the representation of number 42
in Binary is 101010
and in Octal 2a
and in HexaDecimal 52

5- Some Logic operations in java

to represent AND operation we use that symbol &&
to represent OR operation we use that symbol ||
to know the equality we use ==
and to assign a value to variable we use =

6- Ternary operation

The ? : operator is called a ternary operator. It evaluates a condition (before the sign ?) and, if it results in true, assigns to a variable the value calculated by the first expression (between the ? and : signs); otherwise, it assigns the value calculated by the second expression (after the : sign)

int n = 1, m = 2;
float k = n > m ? (n * m + 3) : ((float)n / m);
System.out.println(k);            //prints: 0.5

7- we spoke about typeCasting

if you try to divide integer number on interger number the outPut must be integer.

System.out.println(5/2); //that will print 2

And that is a problem the fraction disappeared !
So if you want to save the fraction you must divide Double or Float on that number

System.out.println(5.0/2); // Wow that's awesome the outPut is 2.5

that we done is called type case, and there is to ways to case from int to double

multiply the number with 1.0
or and (double)before the number

8- finally we spoke about if statement

and the style of write it is

if(condition){
            //do that orders
}

if(condition){
            //if the condition is true do that 
}else{
            // it the condition is false do that 
}

if(condition1){
           //if condition1 is true do that 
}else if(condition2){
           //if condition1 is false and condition2 is true do that 
}else {
           // if there isn't any condition is true do that
}

9- At the end of that session we spoke about loops and forLoop

if you want to repeat some thing many times

for(inti , condition , increment){
      //the thing we want to be repeated
}

example

for (int i = 0; i < 10; i++) {
            System.out.println(i);
}

find the summation of numbers from 1 to n

Scanner sc = new Scanner(System.in);
int number = sc.nextInt(); 
int sum = 0 ;
for(int i = 1; i <= number ; i++){
      sum +=i;
}
System.out.println("The summation of numbers from 1 to "+n+" is equals "+sum);

DEV Community: Abdelrhman khaled

1D Array Revision by java

Great questions need some one to solve

Java HackerRank AUFS Season 6

What we toke in session 2