The Object class and its methods (toString, equals, hashCode, clone, finalize)

Every class in Java implicitly extends java.lang.Object. This means all objects inherit the methods of Object.

Commonly overridden methods:

toString()

Returns a string representation of the object. Default: ClassName@hashcode.

@Override
public String toString() {
    return "Person{name='" + name + "', age=" + age + "}";
}

equals(Object obj)

Compares objects for equality. Default: reference equality (==).

@Override
public boolean equals(Object obj) {
    if (this == obj) return true;
    if (obj == null || getClass() != obj.getClass()) return false;
    Person p = (Person) obj;
    return age == p.age && name.equals(p.name);
}

hashCode()

Returns an integer hash code. Must be consistent with equals: if a.equals(b) then a.hashCode() == b.hashCode().

@Override
public int hashCode() {
    return Objects.hash(name, age);
}

clone()

Creates and returns a copy of the object. Requires implementing Cloneable interface.

@Override
protected Object clone() throws CloneNotSupportedException {
    return super.clone(); // shallow copy
}

finalize()

Called before garbage collection (deprecated since Java 9). Do not use.

Best practices:

• Always override toString() for meaningful object representation.
• Override equals() and hashCode() together (e.g., for use in collections like HashMap).
• Prefer Objects.equals() and Objects.hash() to avoid null checks.