Features of Java

Features of java: -

1.       Simple: - Java is a simple programming language. Learning & practicing java is easy because of its resemblance C and C++ pointers are not available on JAVA.

Why pointers are not available on java?

A)    1. Pointers lead to confusion for a programmer

        2. Pointers easily crash a program.

                       

2.       Object Oriented: - Java is a purely object-oriented programming language. Java programs use objects & classes.

                      

3.       Distributed: - Information is distributed on various on a network. Using java, we can write programs which capture information & distribute it to clients.

4.       Robust: - Robust means strong. Java programs are strong. Java programs will not crash easily because of its execution handling and its memory management features.

5.       Secure: - Java enables the constructions of various free and tamper-free systems.

6.       Architecture Neutral or independent: - Java’s byte code isn’t machine dependent. It can be run any machine with any processor & with any operating system.

7.       Portable: - Java programs give same results on all machines. Everything is clearly defined in java specification & nothing is left to o / s. If the Program is eliding give same results are called portability.

8.       Interpreted: - Java programs are compiled to generate the byte code. This byte code can be downloaded & interpreted by the interpreter in JVM. In java we use interpreter. This interpreter is slow that’s why problem is occurred

9.       High performance: - Along with interpreter, there will be JIT (just in time) compiler which enhance the speed of execution.

10.   High performance: - Along with interpreter, there will be JIT (just in time) compiler which enhance the speed of execution.

11.   Multi-Threaded: - A thread is a process or execution. We can create different processing in java called ‘threads’. This as an essential feature to design server side programs.

12.   Dynamic: - We can develop programs in java which dynamically interact with the user on internet.

Ex: - Applets.

Polymorphism in Java with examples

Polymorphism:-

More than one function with the same is called polymorphism.

There are two types of polymorphisms.

1.      Method overloading (compile time polymorphism).

2.      Method overriding (run time polymorphism).

Method overloading:-

Two or more methods with the same name but difference in methods signatures.

Example:-

void add(int a, int b)  

void add(int a,int b,int c)

  Example program:- 

 public class MethodOverloading {

    public static void main(String args[])

    {

       Sum s=new Sum();

       s.add(10,20);

       s.add(10, 20, 30);

    } 

}

class Sum{

    void add(int a,int b)

    {

               System.out.println("sum of two is"+(a+b));

    }

     void add(int a,int b,int c) {

               System.out.println("sum of three is"+(a+b+c));

    }

}   

Method overriding:-

Two or more methods in super and sub classes with the same name and with same method signatures is called method overriding.

Example:-

public class Boy{

void add(int a,int b){

}

}

class Girl{

void add(int a,int b){

}

}

Example Program:-

public class MethodOverriding {

    public static void main(String args[])

    {

        Sum1 s1=new Sum1();

        s1.add(10, 20);

        s1.add(10, 30);

    }   

}

class Sum1{

    void add(int a,int b){

        System.out.println("sum is:"+(a+b));

    }

}

class Sum2 extends Sum1{

    void add(int a,int b){

        System.out.println("sum is:"+(a+b));

    }

}

Data Types in Java

Data types: -

               A data type represents the type of data stored in variable.

Integer data types: -

These data types represent integer numbers 

Data type                     Memory size                           min and max value

1. byte                           1  Byte                                            - 128 to +127

2. short                           2  Bytes                                 - 32768 to +32767

3. int                               4  Bytes                                 - 21474836 to +2147483647

4. long                            8 Bytes                                  -9223372036854775808 to 

                                                     +9223372036854775807                                                                                                                                                                         

Float data types: - Float means floating point numbers. Float data type represent numbers with decimal points. 

Ex: - 1.5, 3.14159,-2.2, 100.0 etc….

         Float means single precision floating point number. Double means double precision floating point number. Precision means accuracy.

Data type                 Memory size                           min and max value

1) float                       4 bytes                                    1.4e-45 to +3.4e38.

2) double                    8 bytes                                    4.1e-324 to+1.8e308.

 e means into 10 powers. (x 10power).

Character data type: -

Data type                Memories size                          min and max valve

  char                     2 bytes                                        0 to 65535 

     This data type represents a single character. In C or CPP languages using  only one byte in a char.

Ex: -    char ch = ‘x’;

    Single character literal write inside the ‘ ’(single code).

    write string in the double codes (“ ”).

A string represent group of characters.

EX: -                                                                                   

            String name=“narendar reddy”;

ASCII: - American Standard Code for Information Interchange.

Boolean data types: - These data types represent only 2 values either a true or false.

EX: -   boolean response=true;

Operators: - An operator is a symbol that performs on an operation.

EX: -

If an operator acts on a single variable, it is called unary operator.

If an operator acts on a 2 variables, it is called binary operator.

If an operator acts on a 3 variables, it is called ternary operator.

Operators in java: -

1)      Arithmetic operators: - + , - , * , / , %

These operators perform basic arithmetic calculations.

EX: - If a=5, b=5;

                                                     Operator

                        a   +   b

   

         Operands

2) Unary operators: -   - , ++ , --

            These operators act upon a single operand.

àUnary minus ( - ):- This operator negates the value of a variable.

EX:-

            int  x=5;

            System.out.println(-x);             o/p:- -5

            System.out.println(-(-x));        o/p:-  5

Increment (++): - This operator increases the value of a variable by ‘1‘.

EX: - public class UnaryOperator {

    public static void main(String args[])

    {

        int a=10;

        System.out.println(" a is"+a); // a=10

        ++a;

        System.out.println(" a is"+a); //a=11

    }

 }

Writing ++ before a variable is called pre – incrementation

Writing ++ after a variable is called post – incrementation

àWhat is the value of the following expression? Given a=7? ++a * a++?

A) A) 49                      B) 64               C) 72               D) none of these

Decrement (--): - This operator decreases the value of a variable by ‘1‘.

EX: - int x=1;

            --x;       O/P:  0

            x--;       O/P: -1

Writing -- before a variable is called pre – decrementation

Writing -- after a variable is called post – decrementation

3) Assignment operators: -  = , += , -= , *= , /= , %=

            a) This operator is used to store a value in to a variable.

EX: - int x=5;

            b) It is used to store the value of a variable in to another variable.

EX: - int  x=y;

            c) It is used to store the value of an expression in to a variable.

EX: - int x = y + z - 4;

            Expressions mean combination of a variables & values.

Note: - We can not write more than 1 variable at the left side of assignment.

EX: - x + y = 15;   // invalid

4) Relational operator: - < , > , <= , >= , == , !=

            These operators are useful to compare to quantities. They are used in construction of condition.

EX: -

            if(a>b)

           if(a<=b)

5) Logical operators: - &&(and) , | |(or) , !(not)

            These operators are useful to create compound condition. The compound condition is condition of several simple conditions.

EX: -

            If(a>b||b>c||c>d)-----;

                                              

            Any one thing is true this will be executed;

            If(x==10&&y!=10)----;

                                                   

            Both are true this will be executed.

            If(!(x==!))------;

            If(!(x==1 && y==2))----;

6) Boolean operators: - & , | , !

            Boolean operators act upon Boolean variables and they return Boolean result

boolean a,b;

a=true;

b=false;

EX: -

            a & b à false

            a | b   à true

            a & a à true                        boolean type results

            b | b   àfalse

            ! a     à false

            ! b     à true

7) Bitwise operators: -  ~ , & , | , ^ , << , >> , >>>

           These operators act up on individual bits binary digits, (0&1) of numbers.