Composition in Java

1.	Composition in Java
Answer» The two entities in composition are quite dependent on each other i.e. one ENTITY cannot exist without the other. Basically, composition is a restricted form of aggregation. A program that demonstrates composition in Java is given as follows: import java.io.; import java.util.; class DEPARTMENT { public STRING name; Department(String name) { this.name = name; } } class College { private final List<Department> departments; College (List<Department> departments) { this.departments = departments; } public List<Department> getDepartments() { return departments; } } public class Demo { public static void main (String[] args) { Department d1 = new Department("Computer Science"); Department d2 = new Department("Electrical"); Department D3 = new Department("Mechanical"); Department d4 = new Department("INFORMATION Technology"); Department d5 = new Department("Civil"); List<Department> departments = new ArrayList<Department>(); departments.add(d1); departments.add(d2); departments.add(d3); departments.add(d4); departments.add(d5); College c = new College(departments); List<Department> dpt = c.getDepartments(); System.out.println("The different departments in college are: "); for(Department d : dpt) { System.out.println(d.name); } } } The output of the above program is as follows: The different departments in college are: Computer Science Electrical Mechanical Information Technology Civil The above program is an example of composition as the departments and college are dependent on each other. There would be no departments without a college.

Answer»

The two entities in composition are quite dependent on each other i.e. one ENTITY cannot exist without the other. Basically, composition is a restricted form of aggregation.

A program that demonstrates composition in Java is given as follows:

import java.io.*; import java.util.*; class DEPARTMENT { public STRING name; Department(String name) { this.name = name; } } class College { private final List<Department> departments; College (List<Department> departments) { this.departments = departments; } public List<Department> getDepartments() { return departments; } } public class Demo { public static void main (String[] args) { Department d1 = new Department("Computer Science"); Department d2 = new Department("Electrical"); Department D3 = new Department("Mechanical"); Department d4 = new Department("INFORMATION Technology"); Department d5 = new Department("Civil"); List<Department> departments = new ArrayList<Department>(); departments.add(d1); departments.add(d2); departments.add(d3); departments.add(d4); departments.add(d5); College c = new College(departments); List<Department> dpt = c.getDepartments(); System.out.println("The different departments in college are: "); for(Department d : dpt) { System.out.println(d.name); } } }

The output of the above program is as follows:

The different departments in college are: Computer Science Electrical Mechanical Information Technology Civil

The above program is an example of composition as the departments and college are dependent on each other. There would be no departments without a college.

Composition in Java

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