How to override equals method in Java

//Written by K@stackoverflowpublic class Main {    /**     * @param args the command line arguments     */    public static void main(String[] args) {        // TODO code application logic here        ArrayList<Person> people = new ArrayList<Person>();        people.add(new Person("Subash Adhikari", 28));        people.add(new Person("K", 28));        people.add(new Person("StackOverflow", 4));        people.add(new Person("Subash Adhikari", 28));        for (int i = 0; i < people.size() - 1; i++) {            for (int y = i + 1; y <= people.size() - 1; y++) {                boolean check = people.get(i).equals(people.get(y));                System.out.println("-- " + people.get(i).getName() + " - VS - " + people.get(y).getName());                System.out.println(check);            }        }    }}//written by K@stackoverflowpublic class Person {    private String name;    private int age;    public Person(String name, int age){        this.name = name;        this.age = age;    }    @Override    public boolean equals(Object obj) {        if (obj == null) {            return false;        }        if (obj.getClass() != this.getClass()) {            return false;        }        final Person other = (Person) obj;        if ((this.name == null) ? (other.name != null) : !this.name.equals(other.name)) {            return false;        }        if (this.age != other.age) {            return false;        }        return true;    }    @Override    public int hashCode() {        int hash = 3;        hash = 53 * hash + (this.name != null ? this.name.hashCode() : 0);        hash = 53 * hash + this.age;        return hash;    }    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }}

Output:

run:

-- Subash Adhikari - VS - K false

-- Subash Adhikari - VS - StackOverflow false

-- Subash Adhikari - VS - Subash Adhikari true

-- K - VS - StackOverflow false

-- K - VS - Subash Adhikari false

-- StackOverflow - VS - Subash Adhikari false

-- BUILD SUCCESSFUL (total time: 0 seconds)

Introducing a new method signature that changes the parameter types is called overloading:

public boolean equals(People other){

Here People is different than Object.

When a method signature remains the identical to that of its superclass, it is called overriding and the @Override annotation helps distinguish the two at compile-time:

@Overridepublic boolean equals(Object other){

Without seeing the actual declaration of age, it is difficult to say why the error appears.

I'm not sure of the details as you haven't posted the whole code, but:

• remember to override hashCode() as well
• the equals method should have Object, not People as its argument type. At the moment you are overloading, not overriding, the equals method, which probably isn't what you want, especially given that you check its type later.
• you can use instanceof to check it is a People object e.g. if (!(other instanceof People)) { result = false;}
• equals is used for all objects, but not primitives. I think you mean age is an int (primitive), in which case just use ==. Note that an Integer (with a capital 'I') is an Object which should be compared with equals.

See What issues should be considered when overriding equals and hashCode in Java? for more details.