toString method of Object class in java

What is toString() method of object class in java:

The toString method in Java is a member of the Object class and is used to return a string representation of an object.

By default, the toString method provides a string that includes the class name and the memory address of the object.

Default Implementation of toString:

The toString method is defined in the Object class as follows:

Purpose of Overriding toString:

The default implementation is not very informative for most use cases. Therefore, it is common to override the toString method in custom classes to provide meaningful and human-readable information about the object's state.

Example: Default Behavior:

public class Main {

  public static void main(String[] args) 

{ 

  Object obj = new Object();

 System.out.println(obj.toString());

 } 

 }

Output:

java.lang.Object@<hashCode>

The <hashCode> part is the hexadecimal representation of the object's hash code.

Example: Overriding toString

Here's how you might override the toString method in a custom class:

java code:

public class Person {
    private String name;
    private int age;

    // Constructor
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

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

    public static void main(String[] args) {
        Person person = new Person("Alice", 30);
        System.out.println(person); // Calls person.toString() implicitly
    }
}

Output:

Person{name='Alice', age=30}

Explanation of the Code:
Equals Method:

Compares two Person objects for equality based on their name and age fields.

HashCode Method:

Uses Objects.hash() to generate a hash code based on the name and age fields.
This ensures that hashCode is consistent with equals.

Demonstration:

Two Person objects with the same name and age have the same hashCode value and are considered equal.
Different Person objects produce different hash codes.

Key Points:
Consistency:

If the state of an object does not change, the hashCode method should consistently return the same value.
Performance:

A good hashCode implementation minimizes collisions, improving the performance of hash-based collections.

Best Practices:

Use the Objects.hash() utility method for simplicity and reliability when calculating hash codes.
Include the same fields in hashCode as in equals.
This ensures that your custom class works effectively in collections like HashMap or HashSet