Java equals() and hash() example

 

public class TrophyCalculationPayload {
    private List<Integer> playerIds;
    private Integer companyId;
    private Integer gameId;
    private String gameType;
    private Integer point;
    private Integer time;
    private Integer highScore;
    private Integer gameSessionId;
    private String timeZone;
    private Integer servedQuestionCount;
    private Integer correctAnswerCount;

    @Override
    public boolean equals(Object other) {
        if (this == other) {
            System.out.println("first if");
            return true;
        }
        if (other == null || getClass() != other.getClass()) {
            System.out.println("second if");
            return false;
        }

        TrophyCalculationPayload otherPayload = (TrophyCalculationPayload) other;

        if( Objects.equals(companyId, otherPayload.companyId) &&
                Objects.equals(gameId, otherPayload.gameId)) {
            System.out.println("third if");
        }
        return true;
    }

    @Override
    public int hashCode() {
        return Objects.hash(companyId, gameId);
    }
}

 public static void main(String[] args) {
        TrophyCalculationPayload payload= new TrophyCalculationPayload(Arrays.asList(1,2,3),1,1,"game",1,1,1,1,"tz",1,1);
        TrophyCalculationPayload payload1=new TrophyCalculationPayload(Arrays.asList(1,2,3),1,1,"game",1,1,1,1,"tz",1,1);
        TrophyCalculationPayload payload3=payload1;
        String name="pawan";
        String name1="pawan";

        String name2=new String("pawan");
        String name3=new String("pawan");
        System.out.println("--------"+ (name==name1));
        System.out.println("--------"+ name.equals(name1));
        System.out.println("--------"+name2.equals(name3));
        System.out.println("--------"+name.equals(name1));
        System.out.println("--------"+name1.equals(name));
//
        System.out.println("--------"+payload.equals(payload1));
        System.out.println("--------"+payload1.equals(payload3));
        System.out.println("----payload----"+payload.hashCode());
        System.out.println("----payload1----"+payload1.hashCode());

 Note In string class equals() method overided to compare compare content 

 But Object class equals() method overided to compare references.

 So when we compare 

 System.out.println("--------"+ name.equals(name1));

it retuns true;

but when compare User defined class then it return false,because  equals()
default overided behavior is to compare object references.