Answer / shiv prakash

Class must be final
Class must implement Comparable interface(compareTo() method)
Must override hashCode() and equals() methods
Class must implement Serializable interface

For example- all wrapper classes-Integer, Number, Character, and String

Own class
package com;

import java.io.Serializable;

public final class FinalPerson implements Serializable, Comparable<FinalPerson>{

private static final long serialVersionUID = 1L;

private final Integer personId;

private final String name;

private final String city;

private final String gender;

public FinalPerson(final Integer personId, final String name, final String city, final String gender) {
this.personId = personId;
this.name = name;
this.city = city;
this.gender = gender;
}


public Integer getPersonId() {
return personId;
}


public String getCity() {
return city;
}

public String getGender() {
return gender;
}

public String getName() {
return name;
}

@Override
public String toString() {

return "Person- name:"+this.getName()+", City:"+this.getCity()+",gender:"+this.getGender();
}


public int compareTo(FinalPerson p) {

return this.getName().compareTo(p.getName());
}

@Override
public boolean equals(Object obj) {
FinalPerson p = (FinalPerson)obj;
return this.getPersonId().equals(p.getPersonId());
}

@Override
public int hashCode() {
int hash = 7;
hash = 31* hash + this.getPersonId();
return hash;
}



}

Answer / sudha

Map p=new HashMap();
PojoClass pc=new PojoClass();
p.put("key",pc);

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