Package details_ Four access control characters_ Two details of protected

Encapsulation is one of the three characteristics of object-oriented .

The concept of encapsulation ：

High cohesion , Low coupling .

The function and meaning of encapsulation ：

Our programming should pursue ,“ High cohesion , Low coupling ”. High cohesion means that the internal data operation details of a class are completed by themselves , External interference is not allowed , The second coupling is to expose only a small number of methods to external use , Try to facilitate external calls .

4, The specific advantages of being encapsulated in ：

Improve the security of the code

Improve code reusability

“ High cohesion ”： Package details , Easy to modify internal code , Improve maintainability .

“ Low coupling ”： Simplify external calls , Easy for callers to use , Easy to expand and collaborate .

The implementation of encapsulation ---- Use access control

Java It's using “ Access control character ” To control which details need to be encapsulated , What needs to be exposed .

Java in 4 Kind of “ Access control character ” Namely ：pritave( Private )\default（ Illegal ）\protected（ The protected ）\public（ Public ）.

【 notes 】 About protected Two details of :
1. If parent and child are in same package , Subclasses can access the parent class protected member , You can also access the of the parent object
 protected member
2. If subclass and parent are not in same package , Subclasses can access the parent class protected member , Cannot access parent object
Of protected member

Simple rules encapsulated in development :

1. Properties are generally used private Access right .
2. After the property is private , Provide corresponding get/set Method to access related properties , These methods are usually public Embellished , To provide assignment and read operations on properties ( Be careful : boolean Variable get The method is is start !)
3. Method : Some auxiliary methods only used in this class can be used private modification , I hope the methods called by other classes use public modification .

【 Example 】 JavaBean Packaging demonstration of  

public class Person
    ∥ Properties are generally used private modification 
    private String name;
    private int age;
    private boolean flag;    
    ∥ Provide... For properties  public Embellished set/get Method 
    public String getName((
    return name;
    public void setName(String name){
    this.name name;
    public int getAge0
    return age;