Object Class Methods

Every Java class automatically inherits from Object.

class Person {
}

is basically:

class Person extends Object {
}

Common Methods

1. equals()

Checks whether two objects are equal.

Person p1 = new Person();
Person p2 = new Person();

p1.equals(p2); // false

By default, it behaves like ==.

Override equals() when you want to compare object values.

2. hashCode()

Returns a number (hash) representing the object.

p1.hashCode();

If you override equals(), also override hashCode().

3. toString()

Returns a string describing the object.

System.out.println(p1);

By default, you get something like:

Person@5acf9800

You can override it:

@Override
public String toString() {
    return "Person";
}

4. getClass()

Tells you the object's actual class.

System.out.println(p1.getClass());

Output:

class Person

getClass() cannot be overridden.

5. clone()

Creates a copy of an object.

Person copy = (Person) p1.clone();

Requires Cloneable and should be used carefully.

6. finalize()

Was intended for cleanup before garbage collection.

Do not use it. It is deprecated. Use AutoCloseable / try-with-resources instead.

Easy Summary