Lombok - @EqualsAndHashCode

A class definition annotated with @EqualsAndHashCode lets Lombok generate the equals() and hashCode() methods implementation. By default, it'll use all non-static, non-transient fields.

You can also modify which fields are used by marking class fields with @EqualsAndHashCode.Include or @EqualsAndHashCode.Exclude. Alternatively, you can specify exactly which fields or methods you want to be used by marking them with @EqualsAndHashCode.Include and using @EqualsAndHashCode(onlyExplicitlyIncluded = true). Check out the @ToString page for more details about how to configure the generation of the method using those annotations.

Let's take a look at the following example which shows the basic usage of this annotation.

package nl.emsnsoftware.entity;

import lombok.*;

import java.time.LocalDate;

@NoArgsConstructor()
@EqualsAndHashCode
public class Car {
    String licensePlate;
    String brand;
    LocalDate manufacturingDate;
    boolean inUse;
    static int count;
}

And the compiled .class code:

package nl.emsnsoftware.entity;

import java.time.LocalDate;

public class Car {
    String licensePlate;
    String brand;
    LocalDate manufacturingDate;
    boolean inUse;
    static int count;

    public Car() {
    }

    public boolean equals(Object o) {
        if (o == this) {
            return true;
        } else if (!(o instanceof Car)) {
            return false;
        } else {
            Car other = (Car)o;
            if (!other.canEqual(this)) {
                return false;
            } else if (this.inUse != other.inUse) {
                return false;
            } else {
                label49: {
                    Object this$licensePlate = this.licensePlate;
                    Object other$licensePlate = other.licensePlate;
                    if (this$licensePlate == null) {
                        if (other$licensePlate == null) {
                            break label49;
                        }
                    } else if (this$licensePlate.equals(other$licensePlate)) {
                        break label49;
                    }

                    return false;
                }

                Object this$brand = this.brand;
                Object other$brand = other.brand;
                if (this$brand == null) {
                    if (other$brand != null) {
                        return false;
                    }
                } else if (!this$brand.equals(other$brand)) {
                    return false;
                }

                Object this$manufacturingDate = this.manufacturingDate;
                Object other$manufacturingDate = other.manufacturingDate;
                if (this$manufacturingDate == null) {
                    if (other$manufacturingDate != null) {
                        return false;
                    }
                } else if (!this$manufacturingDate.equals(other$manufacturingDate)) {
                    return false;
                }

                return true;
            }
        }
    }

    protected boolean canEqual(Object other) {
        return other instanceof Car;
    }

    public int hashCode() {
        int PRIME = true;
        int result = 1;
        int result = result * 59 + (this.inUse ? 79 : 97);
        Object $licensePlate = this.licensePlate;
        result = result * 59 + ($licensePlate == null ? 43 : $licensePlate.hashCode());
        Object $brand = this.brand;
        result = result * 59 + ($brand == null ? 43 : $brand.hashCode());
        Object $manufacturingDate = this.manufacturingDate;
        result = result * 59 + ($manufacturingDate == null ? 43 : $manufacturingDate.hashCode());
        return result;
    }
}

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