Object

Object is the root superclas of all classes in Java.
Every class in Java implicitly inherits from java.lang.Object.

Why is it important?

• Defines common behaviors for all Java objects.
• Enables Java’s polymorphism, collections and runtime type handling.

Example

Object obj = new String("Hello");
 
System.out.println(obj.toString()); // "Hello"
System.out.println(obj.getClass()); // java.lang.String

Key Points

• You don’t need to extend Object - it happens automatically.
• Override equals(), hashCode() and toString() in custom classes.
• Object allows you to store any type (used in raw collections, generics).

Methods

equals()   // Compares object content (override to customize)
hashCode() // Returns hash value (used in hash-based collections)
toString() // Returns a string representation of the object
getClass() // Returns runtime class info
clone()    // Creates and returns a copy (requires Cloneable)
finalize() // Called by GC before object is destroyed (deprecated)
wait(), notify(), notifyAll() // Thread synchronization methods

Real-World Analogy

Like the base template from which every other object is made. Every tool, shape or widget starts from this base.

Tip

Be ready to answer:

• Why does every class extend Object?
• What’s the use of equals() / hashCode() / toString()?
• What happens if you don’t override them?

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Parent: _OOP