What is a method signature in Java? -Learn Java

What is a method signature in Java? -Learn Java

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In java, method signature consists of name of the method followed by argument types.

Example:

in java return type is not part of the method signature .Compiler will use method signature 

while resolving method calls.

   class Demo

  {

      public void m1(double d){ }

      public void m2(int i)    { }

      public static void main(String args[]){

         Demo d=new Demo();

         d.m1(11.2);

         d.m2(10);

         d.m3();  //CE

    }

  }

CE:cannot find symbol

symbol:method m3(double)

location:class Demo

Within  the same class we cant't take 2 method with the same signature otherwise we will 

get compile time error.

Example:

   public void methodOne() { }

   public int methodOne() { 

    

     return 10;

   }

Output:

Compile time error

methodOne() is already defined in Demo.

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Aggregation in Java: Definition and Examples -Learn Java

Aggregation in Java: Definition and Examples -Learn Java

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Without existing container object if there is a chance of existing contained objects

such type of relationship is called aggregation .

in aggregation objects have weak association.

Example:

Within a department there may be a chance of several professors will work whenever 

we are closing department still there may be a chance of existing department object the

 relationship between department and professor is called aggregation where the objects

 having weak association.

Example:

Composition in Java Example - Learn Java

Composition in Java Example - Learn Java

without existing container object if there is no chance of existing contained object

then the relation between container object and contained object is called composition 

which is a strong association.

Example:

Any university consists of several departments whenever university object destroys automatically 

all the department object will be destroys that is without existing dependent object hence there are associated and this relationship is called composition .

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HAS-A relationship in Java - Learn java

HAS-A relationship in Java - Learn java

1.HAS-A Relationship is also knows as composition(or) aggregation.

2.There is no specific keyword to implement HAS-A relationship but mostly 

    we can use new operator.

3.The main advantage of  reusability.

Example:-

class Engine
{
 // engine functionality
}
class Car
{
   Engine e=new Engine();
  //------------------------------;
  //------------------------------;
  //------------------------------;
}

NOTE:-

class car has-a engine reference.
The main dis-advantage of has-a relationship increases dependency between the
components and creates maintains problems.


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