| Types java app |
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| Data Types and Operators |
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| (Primitive Data Types) |
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| (Non-Primitive Data Types) |
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| Control Flow Statements |
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| Conditional Statements |
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| Looping Statements |
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| Branching Statements |
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| Object-Oriented Programming (OOP) |
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| Classes and Objects |
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| Inheritance |
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| Polymorphism |
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| Encapsulation |
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| Abstraction |
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| Exception Handling |
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| Introduction to Exceptions |
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| Collections Framework |
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| Overview of Collections |
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| Commonly Used Collections |
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| Iterators |
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| Java I/O |
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| File Handling |
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| Serialization |
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| Multithreading |
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| Introduction to Threads |
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| Thread Synchronization |
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| GUI Programming with Swing |
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| Introduction to Swing |
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| Event Handling |
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| Advanced Topics |
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| Java Database Connectivity (JDBC) |
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| JAVA CODE |
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Java Basics
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Working with Objects
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Arrays, Conditionals, and Loops
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Creating Classes and Applications in Java
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More About Methods
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Java Applet Basics
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Graphics, Fonts, and Color
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Simple Animation and Threads
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More Animation, Images, and Sound
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Managing Simple Events and Interactivity
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Creating User Interfaces with the awt
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Windows, Networking, and Other Tidbits
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Modifiers, Access Control, and Class Design
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Packages and Interfaces
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Exceptions
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Multithreading
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Streams and I/O
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Using Native Methods and Libraries
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Under the Hood
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Java Programming Tools
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Working with Data Structures in Java
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Advanced Animation and Media
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Fun with Image Filters
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Client/Server Networking in Java
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Emerging Technologies
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appendix A :- Language Summary
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appendix B :- Class Hierarchy Diagrams
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appendix C The Java Class Library
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appendix D Bytecodes Reference
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appendix E java.applet Package Reference
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appendix F java.awt Package Reference
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appendix G java.awt.image Package Reference
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appendix H java.awt.peer Package Reference
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appendix I java.io Package Reference
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appendix J java.lang Package Reference
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appendix K java.net Package Reference
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appendix L java.util Package Reference
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In Java, getters and setters are methods used to access and update the values of private instance variables. They are a fundamental concept in encapsulation, a core principle of object-oriented programming (OOP). Encapsulation ensures that the internal state of an object is protected from unauthorized access and modification.
Encapsulation in Java
Encapsulation involves:
- Declaring instance variables as private: This restricts direct access to these variables from outside the class.
- Providing public getter and setter methods: These methods allow controlled access to the variables.
Getters
Getters are methods used to retrieve the value of a private instance variable. A getter method typically starts with the prefix get followed by the variable name with the first letter capitalized.
Example of a Getter:
public class Person {
private String name;
private int age;
// Getter for name
public String getName() {
return name;
}
// Getter for age
public int getAge() {
return age;
}
}
Setters
Setters are methods used to update the value of a private instance variable. A setter method typically starts with the prefix set followed by the variable name with the first letter capitalized.
Example of a Setter:
public class Person {
private String name;
private int age;
// Setter for name
public void setName(String name) {
this.name = name;
}
// Setter for age
public void setAge(int age) {
if(age > 0) { // simple validation
this.age = age;
}
}
}
Detailed Explanation
Access Control: By making instance variables private, you restrict direct access from outside the class. Getters and setters provide controlled access, allowing you to add logic for validation, logging, or other operations when getting or setting a value.
Encapsulation and Abstraction: Encapsulation hides the internal implementation details from the outside world. With getters and setters, you can change the internal representation of a variable without changing the external interface. This is useful for maintaining and updating code.
Validation and Logic: Setters can include validation logic to ensure that the object’s state remains consistent. For example, you might want to ensure that an age value is positive.
Immutability: In some cases, you might not provide a setter, making the variable effectively read-only from outside the class. This can help create immutable objects.
Framework Compatibility: Many Java frameworks, such as JavaBeans, rely on the presence of getters and setters to function correctly. They use reflection to call these methods dynamically.
Best Practices
Keep Getters and Setters Simple: Avoid adding complex logic in getters and setters. If you need complex logic, consider using separate methods.
Use Meaningful Names: Follow standard naming conventions to make your code more readable and maintainable.
Validation in Setters: Always validate the input parameters in setters to ensure the object’s state remains valid.
Consider Immutability: For objects that should not change once created, provide getters but not setters, or use a builder pattern.
Example Class with Getters and Setters
public class Car {
private String model;
private int year;
// Constructor
public Car(String model, int year) {
this.model = model;
this.year = year;
}
// Getter for model
public String getModel() {
return model;
}
// Setter for model
public void setModel(String model) {
this.model = model;
}
// Getter for year
public int getYear() {
return year;
}
// Setter for year with validation
public void setYear(int year) {
if (year > 1885) { // The first car was invented around 1886
this.year = year;
} else {
throw new IllegalArgumentException("Year must be greater than 1885");
}
}
public static void main(String[] args) {
Car myCar = new Car("Toyota", 2020);
System.out.println("Model: " + myCar.getModel()); // Output: Toyota
System.out.println("Year: " + myCar.getYear()); // Output: 2020
myCar.setModel("Honda");
myCar.setYear(2022);
System.out.println("Updated Model: " + myCar.getModel()); // Output: Honda
System.out.println("Updated Year: " + myCar.getYear()); // Output: 2022
}
}
In this example, the Car class has private instance variables model and year. It provides public getters and setters for these variables, with validation logic in the setter for year. This ensures that the internal state of a Car object is managed and validated properly.
