Java

To check if you have Java installed on a Windows PC run following command in command prompt (cmd.exe)

java -version

If you do not have Java installed on computer, we can download it for free from oracle.com(Java).

Write Java code in a text editor.

it is possible to write Java in an Integrated Development Environment, such as

IntelliJ IDEA,

Netbeans or

Eclipse, particularly useful for managing larger collections of Java files.

Type        Size        Range

byte           8       -128..127

short         16      -32,768..32,767

int             32      -2,147, 483, 648..2, 147, 483, 647

long          64        9,223, 372, 036, 854, 808..9, 223..

float          32         3.4 e-0.38..3.4e+0.38

double     64         1.7e-308..1.7e+308

char         16         Complete Unicode Character Set

Boolean    |           True, False

Type                           Operators

Arithmetic                    +,-,*,?,%

Assignment                  =,+=,-=,*=,/=,%=,&=,^=,|=,<<=, >>=, >>>=

Bitwise                         ^,&,|

Logical                   &&,||

Relational                    <,>,<=,>=,==,!=

Shift                          <<,>>,>>>

Ternary                        ?:

Unary                      ++x, -x, x++, x-, +x, -x, !, ~

{public | private} [static] type name [= expression | value];

{public | private} [static] {type | void} name(arg1, ...,argN ) {statements}

// Widening (byte<short<int<long<float<double)

int i = 10; //int--> long

long l = i; //automatic type conversation

// Narrowing

double d = 10.02;

long l = (long)d; //explicit type casting

// Numeric values to String

String str = String.valueOf(value);

// String to Numeric values

int i = Integer.parseInt(str);

double d = Double.parseDouble(str);

// Using BufferReader

BufferedReader reader = new BufferedReader (new InputStreamReader (System.in));

String name = reader.readLine();

// Using Scanner

Scanner in = new Scanner(System.in);

String s = in.nextLine();

int a = in.nextInt();

// Using Console

String name = System.console().readLine();

// for loop

for (condition) {expression}

// for each loop

for (int i: someArray) {}

// while loop

while (condition) {expression}

// do while loop

do {expression} while(condition)

for (i = 1; i <= n; ++i)

    {

        System.out.print(t1 + " + " );

        int sum = t1 + t2; t1 = t2;

        t2 = sum;

    }

k = 2*n - 2;

for (i = 0; i < n; i++)

{

    for (j=0; j<k; j++) {System.out.print(" ");}

    k = k - 1;

    for(J=0; j<=i; j++ ) {System.out.print("*");}

    System.out.printIn();

}

//if statement

if (condition) {expression}

//if-else statement

if (condition) {expression} else {expression}

//switch statement

switch (var) { case 1: expression; break;

default: expression; break; }

if (n < 2)

    {

      return false;

    }

    for (int i = 2; i <= n/i; i++)

    {

      if (n%i == 0) return false;

    }

return true;

int factorial(int n)

{

    if(n == 0)

    {return 1;}

    else

    {

    return(n * factorial(n-1));

    }

}

1 - Dimensional

// Intializing

type [ ] varName= new type [size];

// Declaring

type [ ] varName= new type [ ] type {values1, value2,...};

Array with Random Variables

double[ ] arr = new double [n];

for (int i=0; i<n; i++)

{a[i] = Math.random();} 

Maximum value in an Array

double max = 0;

for (int i = 0; i<arr.length(); i++)

{ if(a[i] > max) max = a[i]; }

Reversing an Array

for(int i=0; i<(arr.length())/2; i++)

{ double temp = a[i];

a[i] = a[n-1-i];

a[n-1-i] = temp;}

// Initializing

datatype[ ] [ ] varName = new dataType[row] [col];

//Declaring

datatype[ ] [ ] varName = {{value1, value2....},{value1, value2....}..};

Transposing A Matrix

for(i = 0; i < row; i++)

 { for(j = 0; j < column; j++)

   {System.out.print(array[i][j]+" "); }

System.out.println(" ");

}

Multiplying two Matrices

for (i = 0; i < row1; i++)

    { for (j = 0; j < col2; j++)

      { for (k = 0; k < row2; k++)

        { sum = sum + first[i] [k]*second[k][j]; }

      multiply[i][j] = sum;

    sum = 0; } }

// Creating String using literal

    String str1 = "Welcome";

// Creating String using new keyword

    String str2 = new String("Webenit");

str1==str2 //compare the address;

String newStr = str1.equals(str2); //compares the values

String newStr = str1.equalsIgnoreCase() //

newStr = str1.length() //calculates length

newStr = str1.charAt(i) //extract i' th character

newStr = str1.toUpperCase() //returns string in ALL CAPS

newStr = str1.toLowerCase() //returns string in ALL LOWERCASE

newStr = str1.replace(oldVal, newVal) //search and replace

newStr = str1.trim() // trims surrounding whitespace

newStr = str1.contains("value"); // Check for the values

newStr = str1.toCharArray(); //Convert into character array

newStr = str1.IsEmpty(); //Check for empty String

newStr = str1.endsWith(); // Check if string ends with the given suffix

public class Demo

   {

    public static void main(String[] args)

     {

       System.out.println("Hello from Webenit!");

     }

   }