CORE JAVA (ch-2 DATA TYPE/SETTING PATH)

Hey!guys,this is hitesh..and in the second chapter we'll discuss about data types in java and we'll also learn about path setting for java so that we can execute our programs.

Data Types in Java

1.     byte                1 byte

2.     short              2 byte

3.     int                   4 byte

4.     long                8 bytes

5.     float               4 bytes

6.     double           8 bytes

7.     boolean         undefined (Java Black Book – 2 bytes)

8.     char                2 bytes

Note: all are signed

Data inside the variables

1.     Literals

2.     Interactive Input

3.     Non-interactive input

4.     File Input

5.     Database input

Literals

The values that we use from our side for some assignment or expression are called as literals.

Example

int num=6;

double ar=3.14*num*num;

Literals can be of different types

1.     Integrals

2.     Floatings

3.     Characters

4.     Strings

5.     Booleans

Integrals

By default such numbers take size of int.

Use l or L with long as suffix

int num=6;

long num=6L;

Integral Literals can be of four types

1.     Decimal – 0 to 9, default

2.     Octal – 0 to 7, starts with 0

3.     Hexa – 0 to 9, A to F, Starts with 0x or 0X

4.     Binary – 0 and 1, starts with 0b or 0B

Example

//Sample.jar

class First

{

            public static void main(String args[])

            {

                        int x=6789; //decimal

                        int y=03456; //octal

                        int z=0X8D5; //hexa

                        int p=0b101011; //binary

                        System.out.println(x);

                        System.out.println(y);

                        System.out.println(z);

                        System.out.println(p);

                       

            }

}

Compile the program using JDK software with JAVAC compiler provided inside the BIN folder of the JDK

Syntax

JAVAC <programname>

Example

JAVAC Sample.java à First.class

Now run the class file

JAVA First

Note

If your BIN folder is not set in the PATH the JAVAC and JAVA will not work.

We need to set the PATH

PATH=C:\Program Files\Java\jdk1.8.0_05\bin

If you want to set the path for one time only use the following steps

My Computer à  Properties à Advance System Settings à Advanced à
Environmental Variables à System Variables à Path à Edit…

Now paste the PATH after the semicolon

Note

We can also use underscore (_) as number separator

//Sample.java

class First

{

            public static void main(String args[])

            {

                        int x=12_67_899; //decimal

                        int y=07; //octal

                        int z=0X8D5; //hexa

                        int p=0b10_1011; //binary

                        System.out.println(x);

                        System.out.println(y);

                        System.out.println(z);

                        System.out.println(p);

                       

            }

}

Floating Literals

All numbers with decimal point are of double type by default. Use f or F with float.

double n=6.7;

float x=5.6; //error

float x=5.6f; //correct

Example

class Second

{

            public static void main(String... args)

            {

                        float x=5.6f;

                        System.out.println(x);

            }

}

Note:

A program name and class name can be same or different but if a class is public then both must be same.

Character Literals

Enclosed in single quotes and every character has corresponding ASCII value

char ch=’A’;

or

char ch=65;

String Literals

Enclosed in double quotes and managed by String class.

String name=”Rohit”;

Now we can use basic string methods on name.

Example

class Third

{

            public static void main(String args[])

            {

                        String name="Vikas Kumar Singh";

                        System.out.println("Name is : "+name);

                        System.out.println(name.toUpperCase());

                        System.out.println(name.toLowerCase());

                        System.out.println(name.length());

            }

}

Boolean Literals

Can have only two values

1.     true

2.     false

boolean married=true;

That's all about the data types in JAVA

In the next post we'll discuss about taking input from user with buffered reader,and scanner class with some more packages and we'll also learn about Classes and objects.

Thank You 

Keep learning :)

Keep Coding ;)