HashSetUserDefinedObjectExample.java

importjava.util.HashSet;
importjava.util.Objects;
importjava.util.Set;

classCustomer {
privatelongid;
privateStringname;

publicCustomer(longid, Stringname) {
this.id = id;
this.name = name;
 }

publiclonggetId() {
returnid;
 }

publicvoidsetId(longid) {
this.id = id;
 }

publicStringgetName() {
returnname;
 }

publicvoidsetName(Stringname) {
this.name = name;
 }

@Override
publicbooleanequals(Objecto) {
if (this == o) returntrue;
if (o == null || getClass() != o.getClass()) returnfalse;
Customercustomer = (Customer) o;
returnid == customer.id;
 }

@Override
publicinthashCode() {
returnObjects.hash(id);
 }

@Override
publicStringtoString() {
return"Customer{" +
"id=" + id +
", name='" + name + '\'' +
'}';
 }
}

publicclassHashSetUserDefinedObjectExample {
publicstaticvoidmain(String[] args) {
Set<Customer> customers = newHashSet<>();
customers.add(newCustomer(101, "Rajeev"));
customers.add(newCustomer(102, "Sachin"));
customers.add(newCustomer(103, "Chris"));

/*
 HashSet will use the `equals()` & `hashCode()` implementations
 of the Customer class to check for duplicates and ignore them
 */
customers.add(newCustomer(101, "Rajeev"));

System.out.println(customers);
 }
}