Overview
- Object
- Class
- System
- String Classes
- Arrays
- Boxing & Unboxing
- Varargs
- format & printfMethods
Object
- java.lang.Object
- Represents a Java Object
- All classes are descendants of Object Class.
- Some methods
- protected Object clone()
- public Boolean equals()
- protected void finalize()
Characteristics
- Identity: Each object has a unique identity.
- State: Objects have attributes that define their current state.
- Behavior: Objects can perform actions (methods) based on their class’s behavior definition.
Creating Objects
- To create an object, you use the new keyword followed by a constructor of the class.
- Example:
Car myCar = new Car("Red", "Toyota", "Camry");
Accessing Members
- You can access an object’s attributes and methods using the dot notation.
- Example:
String carColor = myCar.color;
// Accessing an attribute
myCar.startEngine();
// Calling a method
Class
- java.lang.Class
- Gets created whenever JVM creates an object.
- All instances of a class, share this created object of java.lang.Class
- Methods
- public static Class forName(“String className”)
) - public Object newInstance()
- public static Class forName(“String className”)
Characteristics
- Attributes (Fields/Properties): These are data members or variables that represent the characteristics or state of an object. For example, in a Car class, attributes could include color, make, and model.
- Methods (Functions/Operations): These are functions or methods that define the behavior or actions that objects of the class can perform. For example, in a Car class, methods could include startEngine(), accelerate(), and brake().
- Example:
class Car {
// Attributes
String color;
String make;
String model;
// Constructor
public Car(String color, String make,
String model) {
this.color = color;
this.make = make;
this.model = model;
}
// Methods
public void startEngine() {
// Code to start the car's engine
}
public void accelerate() {
// Code to accelerate the car
}
public void brake() {
// Code to apply the brakes
}
}
Java provides a rich set of core classes that are part of the Java Standard Library (also known as the Java API).
