Hi friend,


Association
It is a relationship between classes of objects which allows one object instance to cause another
to perform an action on its behalf. This relationship is structural,
because it specifies that objects of one kind are connected to objects of another.

Aggregation:

In aggregation , one object is composed of multiple objects and
every object is useless without the relationship.
Suppose there is a car object,
so car object is useless without the tyre or steering object,
and steering object is useless without car.
This type of relationship is called Aggregation.

Thanks

Hi friend,

Aggregation is a special kind of association that specifies a whole/part relationship between the aggregate (whole) and a component part. When compared to an ordinary association, some distinguishing characteristics of aggregation include:

* aggregation is an asymmetric relationship
* aggregation is a transitive relationship
* aggregation implies stronger coupling
* behavior (copy, delete, etc.) is normally propagated across an aggregation.


Aggregation is one of two fundamental possibilites to build new classes from existing ones.

public class throwtest {
public static void main(String argv[]) {
int i;
try {
i = Integer.parseInt(argv[0]);
}
catch (ArrayIndexOutOfBoundsException e) {
System.out.println("Must specify an argument");
return;
}
catch (NumberFormatException e) {
System.out.println("Must specify an integer argument.");
return;
}

addValue(i);
}
public static void addValue(int i) {
try {
b(i);
}
catch (MyException e) {
if (e instanceof MySubException)
System.out.print("MySubException: ");
else
System.out.print("MyException: ");
System.out.println(e.getMessage());
System.out.println("Handled at point 1");
}
}
public static void b(int i) throws MyException {
int result;
try {
System.out.println("Enter number is = " + i + ".");
result = c(i);
System.out.println("Add Result is = " + result +".");
}
catch (Exception e) {
System.out.println("Exception: " + e.getMessage());
System.out.println("Handled at point 2");
}
finally {
System.out.print("\n");
}
}
public static int c(int i) throws MyException, MyOtherException {
switch (i) {
case 0:
throw new MyException("input is low");
case 1:
throw new MySubException("input still too low");
case 120:
throw new MyOtherException("input is high");
default:
return i+ i;
}
}
}

-----------------------------------

Thanks.