LinkList (Java)

Java Linked List class uses doubly linked list to store the elements.

The important points about Java Linked List are:

• Java Linked List class can contain duplicate elements.
• Java Linked List class maintains insertion order.
• Java Linked List class is non synchronized.
• In Java Linked List class, manipulation is fast because no shifting needs to be occurred.
• Java Linked List class can be used as list, stack or queue.                                                            Syntax:-                                                                                                                                                      Link List<string>name=new Linked List<string>();                                                                                  {

………………………..    (Description)                                                                                                                                        }                                                                                                                                                                                Example:-
Public Class MyClass
{
pulic static void main(string[] args)
{
LinkList<string>name=new LinkedList<string>();
name.add(“ABC”);      //Add a name in LinkList
name.add(“PQR”);     //Add a name in LinkList
name.add(“XYZ”);     //Add a name in LinkList
for(string:name)
System.out.println(x);
name.addfirst(“Jack”);     //Add First name in LinkList.
name.addlast(“Zack”);     //Add Last name in LinkList.
name.removelast();            //Remove  First name in LinkList.
name.removefirst();         // Remove Last name in LinkList.
name.clear();                    //Delete all the data in LinkList.
System.out.println(name.size());
name.add(index,”element”);      //This is a syntax for add a variable of particular position in LinkList.
name.add(2,”Index”);
name.remove(2);     // Remove a variable of particular position in LinkList
name.set(1,”a”);  //Change a name as particular index.
}
}

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ArrayList

Array List:-ArrayList class uses a dynamic array for storing the elements.

Example:-Public Class MyClass
{
public static void main(string[] args)
{
int single_array=new int[5];   OR {1,2,3,4,5}
ArrayList<Integer>MyList=newArrayList<Integer>(5);
MyList.add(1);
MyList.add(5);
for(Integer x:MyList)
MyList.remove(2);   //To remove index size
MyList.clear();   //to clear index size
System.out.println(x);
System.out.println(MyList.Size());
}
}

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Interface

• An interface in java is a blueprint of a class. It has static constants and abstract methods.
• The interface in java is a mechanism to achieve abstraction. There can be only abstract methods in the java interface not method body. It is used to achieve abstraction and multiple inheritance in Java.
• Java Interface also represents IS-A relationship.
• It cannot be instantiated just like abstract class.
• There are mainly three reasons to use interface. They are given below.

• It is used to achieve abstraction.
• By interface, we can support the functionality of multiple inheritance.
• It can be used to achieve loose coupling.

Class to Class derive–extends
Interface to Class derive–implement
Interface to Interface derive–extends

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Abstract Class

• A class that is declared with abstract keyword, is known as abstract class in java. It can have abstract and non-abstract methods (method with body).
• A method that is declared as abstract and does not have implementation is known as abstract method.

Syntax:-
abstract class A
{
}
Example:-
abstract class Bike    //Abstract Class
{
abstract void run();   //Abstract Method
}
class Honda4 extends Bike
{
void run()
{
System.out.println(“running safely..”);
}
public static void main(String args[])
{
Bike obj = new Honda4();
obj.run();
}
}

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Method Overriding

• If subclass (child class) has the same method as declared in the parent class, it is known as method overriding in java.

Usage:-

• Method overriding is used to provide specific implementation of a method that is already provided by its super class.
• Method overriding is used for runtime polymorphism
  Rules for Java Method Overriding:-
• method must have same name as in the parent class
• method must have same parameter as in the parent class.
• must be IS-A relationship (inheritance).
  Example:–

class Vehicle
{
void run()
{
System.out.println(“Vehicle is running”);
}
}
class Bike2 extends Vehicle
{
void run()
{
System.out.println(“Bike is running safely”);   //Method Overriding
}
public static void main(String args[])
{
Bike2 obj = new Bike2();
obj.run();
}

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Polymorphism

Polymorphism in java is a concept by which we can perform a single action by different ways. Polymorphism is derived from 2 greek words: poly and morphs. The word “poly” means many and “morphs” means forms. So polymorphism means many forms.
 

There are two types of polymorphism in java: compile time polymorphism and runtime polymorphism. We can perform polymorphism in java by method overloading and method overriding.

Runtime Polymorphism in Java:-

Runtime polymorphism or Dynamic Method Dispatch is a process in which a call to an overridden method is resolved at runtime rather than compile-time.

Example:-
Public Class BANK
{
int getInsterestRate()
{
return 0;
}
}

---

Public Class BANK_ABC extends BANK
{
int getInsterestRate()
{
return 0;
}
}

---

Public Class MyClass
{
public static void main(string[] args)
{
BANK abc=new BANK_ABC();
System.out.println(abc.getInsterestRate());
}
}

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Inheritance

Inheritance in java is a mechanism in which one object acquires all the properties and behaviors of parent object.

For Method Overriding (so runtime polymorphism can be achieved).

• For Code Reusability.
  
  
  Syntax :-
  class Subclass-name extends Superclass-name                                         {                                                                                                                                //methods and fields                                                                                                                                    }
  –> The extends keyword indicates that you are making a new class that derives from an existing class. The meaning of “extends” is to increase the functionality.
  
  –> In the terminology of Java, a class which is inherited is called parent or super class and the new class is called child or subclass.
  Type of Inheritance :-
• 

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Final Keyword

A final keyword has a numerous way to use. 

A final class cannot be subclassed. 

A final method cannot be overridden by sub classes. 

A final variable can apply only be initialized once.

Example:-
public Class Hello
{
public final int number;
{
Hello() //Use a constructor
{
number=10;
}
}

---

Public Class MyClass
{
public static void main(string[] args)
{
Hello hel=new Hello();    //Use a Hello Class
hel.number=20;
}
}

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Access Modifier

• The access modifiers in java specifies accessibility (scope) of a data member, method, constructor or class.
• There are 3 types of java access modifiers:

1. private
2. protected
3. public

• Private:-The private access modifier is accessible only within class.
•  Protected:-The protected access modifier is accessible within package and outside the package but through inheritance only.The protected access modifier can be applied on the data member, method and constructor. It can’t be applied on the class.
• Public:-The public access modifier is accessible everywhere. It has the widest scope among all other modifiers.Let’s understand the access modifiers by a simple table.

Access Modifier	within class	within package	outside package by subclass only	outside package
Private	Y	N	N	N
Default	Y	Y	N	N
Protected	Y	Y	Y	N
Public	Y	Y	Y	Y

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Static Keyword

The static keyword in java is used for memory management mainly. We can apply java static keyword with variables, methods, blocks and nested class.

The static keyword belongs to the class than instance of the class.

Example:-
public Class MyClass
{
public static void main(string[] args)
{
Hello.hello=new Hello();
hello.age=10;
Hello.Dosomething(“Hi CastorClasses”);
}
}

---

public Class Hello
{
Static int age;
public static string Dosomething(string message)
return message;
}
public string Dosomething(string message)
return message;
}
}

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Method Overloading

 If a class has multiple methods having same name but different in parameters, it is known as Method  Overloading.

If we have to perform only one operation, having same name of the methods increases the readability of the program.

Example:-
Public Class MyClass
{
public static void main(string[] args)
{
System.out.println Add(1,36);
System.out.println Add(5.65,40.65);
System.out.println Add(“Hello”,”World”);
}
public static int Add(int a,int b)
{
return(a+b);
}
public static double Add(double a,double b)
{
return(a+b);
}
public static string Add(string a,string b)
{
return(a+b);
}
}

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Class

• Class is a key-word, It is a user-defined function.
• Every java program one class and one main methods.

Example:-
Public Class MyClass
{
public static void main(string[] args)
{
int a=10;
int b=20;
int c=a+b;
System.out.println(“Answer=”c);
}
}

Class Constructor

• Class Constructor name is same as class name.
• It is a member method,never return any value define multiple constructor.

Example:-
Main Class–
Public Class MyClass
{
public static void main(string[] args)
{
Cube cube1=new cube();
}
}

---

public class Cube
{
int length;
int breath;
int height;
public int get cube volume()
{
return( length* breath*height);
}
Cube()  //Constructor—> This is same class name
{
System.out.println(“Welcome CastorClasses”);
}

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Parameter

 

• There are two types of parameter .
•  Passing Parameter

• . Returning Methods

Example:-
public class MyClass
{
public static void main(string[] args)
{
CastorClass(“Online”)
public static void CastorClass(string name)
{
System.out.println(“Online Class” +name); //This is a passing parameter .
}
}

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Method

 

• It is called as “Function”. Methods is pieces of code,which execute some logic.

Syntax:-
function()
{
}

Example:-
public class MyClass
{
public static void main(string[] arg)       //Here “main” is a method or function.
{
Myfirstmethods();   //Call method
}
public static void Myfirstmethods()  
{
System.out.println(“Hello CastorClass”);
}
}

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String

• String is a sequence of character and character of array.

Syntax:-

• string mystring=”Hello World”;

{
}

• int mystring length=mystring.length();      // For find a length of string
• string mystring in lowercase=my string . to lowercase();    //To convert uppercase to lowercase
• string mystring in upperrcase=my string . to uppercase();   //To convert lowercase to uppercase.
• string mystring=”Hello + World”;       //
•    System.out.println(mystring.replace(‘e’ , ‘a’));     //to replace the word.

Example:-
public class MyClass
{
public static void main(string[] arg)
{
string mystring=”Hello World”;
System.out.println(“Mystring”);
}
}

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Arrays in Java

• Array is a same as a variable.
• This is add more then one value at a time.

Syntax:-
int[] myintarray={};
{
}

---

Example:-
public class MyClass
{
public static void main(string[] arg)
{
int[]Myintarray={1,2,3,4,5}
//int myintarray[]={1,2,3,4,5}
{
System.out.println(3);
}
}
}

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Loop Structure in java

Loops :

A loop statement allows us to execute a statement or group of statements multiple times and following is the general form of a loop statement in most of the programming languages.

 

1. While loop :- Repeats a statement or group of statements while a given condition is true. It tests the condition before executing the loop body.

 

Syntax :

 

while (boolean condition)

{

// loop statement.....

}

 

 

Example :

 

Class Technogeeks

{

public static void main(String arg[])

{

int x=1;

while (x<=4)

{

System.out.println("Value of x is" +x);

x++;

}

}

}

 

2. do While loop :- Like a while statement, except that it tests the condition at the end of the loop body.

 

Syntax :

 

do

{

   // Ststements......

}

while (condition);

 

 

Example :

 

class Technogeeks

{

public static void main(String args[])

{

int x = 21;

do

{

System.out.println("Value of x is" +x);

x++;

}

while (x<20);

}

}

 

3. For loop :- Execute a sequence of statements multiple times and abbreviates the code that manages the loop variable.

 

Syntax :

 

for(initialization condition; texting condition ; increment/decrement)

{

//Statements

}

 

Example :

 

Class Technogeeks

{

public static void main (String args[])

{

for(int x=2; x<=4; x++)

System.out.println("Value of x is " +x);

}

}

 

 

Infinite Loop

 

Example :

 

public class Technogeeks

{

public static void main(String[] args)

{

for(int i=5; i!=0; i -=2)

{

System.out.println(i);

}

int x=5;

While(x==5)

{

System.out.println("In the loop");

}

}

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Switch Statement

 We will explain a Switch statement is —

The syntax of switch case is : 

Syntax:-
switch()
{
case1:
statement()
break;
case2:
statement()
break;
default:
statement()
break;
}

---

Example:-
public class MyClass
{
public static void main(string[] arg)
{
int score=90;
switch(score)
{
Case 90:
System.out println(“Very good”);
break;
Case 60:
System.out println(“Good”);
break;
Case 40:
System.out println(“OK”);
break;
default:
System.out println(“The grade is not valid”);
}
}
}

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Logical Operator

In logical operator there are two operator

"&&" This is called as AND operator.
 "||" This is called as OR operator.

Example:-
public Class MyClass
{
public static void main(string[] arg)
{
int sub1=50;
int sub2=30;
if((sub1>=35)&&(sub2>=25))||((sub1<=60)&&(sub2<=40))
{
System.out.println(“The condition is true”);
}
else
{
System.out.println(“The condition is false”);
}
}
}

Here, perform a Logical operator.

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