OOPs-inheritance: What is composition in java?

Composition is a technique to implement has-a relationship between classes. We can use java inheritance or Object composition to make our code reusable. Java composition is implemented by using instance variables that refers to other objects. Let´s consider an example in which two classes named Job and Person. Person has the reference of the Job class(We can say that Each person had a job):


Job.java:
-----------------

public class Job {
private String role;
private long salary;
private int id;

public String getRole() {
return role;
}
public void setRole(String role) {
this.role = role;
}
public long getSalary() {
return salary;
}
public void setSalary(long salary) {
this.salary = salary;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}


}


Person.java:
---------------------

public class Person {

//composition has-a relationship
private Job job;

public Person(){
this.job=new Job();
job.setSalary(1000L);
}
public long getSalary() {
return job.getSalary();
}

}