OOP AND ENCAPSULATION

equals() Method Behavior

When a class does not override equals() from Object, .equals() compares references, just like ==.

class Person {
    String name;
    Person(String name) { this.name = name; }
    // No equals() override - inherits Object.equals()
}

Person a = new Person("John");
Person b = new Person("John");
Person c = a;

System.out.println(a.equals(b));  // false - different objects
System.out.println(a == b);       // false - different objects  
System.out.println(a.equals(c));  // true - same reference
System.out.println(a == c);       // true - same reference

// Compare with String (which DOES override equals):
String s1 = new String("hello");
String s2 = new String("hello");
System.out.println(s1.equals(s2)); // true - content comparison
System.out.println(s1 == s2);      // false - different objects

Examples of classes that DON’T override equals():

StringBuilder - reference comparison only
StringBuffer - reference comparison only
Most custom classes (unless explicitly overridden)

💡 Learning Tip: Classes that don’t override equals() are doing reference comparison. StringBuilder is a famous example!