What do you know about the Object class?

java.lang.Object is the root class in the Java class hierarchy. Every class implicitly inherits from Object.

Main methods:

• equals(Object obj): Compares the current object with another object for equality. By default, compares references.
• hashCode(): Returns the hash code of the object. Used in hash-based collections (e.g., HashMap, HashSet). If two objects are equal according to equals(), their hashCode() must be the same.
• toString(): Returns a string representation of the object. By default, returns the class name + @ + hash code in hexadecimal format. Usually overridden to provide more informative output.
• getClass(): Returns the Class object representing the runtime class of the object.
• notify(): Resumes a thread waiting on this object's monitor.
• notifyAll(): Resumes all threads waiting on this object's monitor.
• wait() / wait(long timeout) / wait(long timeout, int nanos): Causes the current thread to wait until another thread calls notify() or notifyAll() on this object, or the specified timeout expires. Called only within synchronized blocks or methods.
• clone(): Creates and returns a copy of this object. Requires implementation of the Cloneable interface.
• finalize(): Called by the garbage collector before the object is removed. Not recommended for use due to unpredictability.

Example of overriding equals() and hashCode():

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 o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Person person = (Person) o;
        return age == person.age &&
               Objects.equals(name, person.name);
    }

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

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

The Object class provides fundamental mechanisms necessary for working with objects in Java, such as comparison, hashing, thread synchronization, and obtaining class information.