Java封装 java封装|Java

【Java封装】包封在Java是包装代码和数据一起成一个单一的单元，例如，它是混合的几种药物的胶囊的方法。
我们可以通过使私有类的所有数据成员在Java中创建一个完全封装类。现在我们可以使用setter和getter方法来设置，并在其中获得数据。
在Java Bean类是完全封装的类的实例。
在Java中封装的优势
通过只提供一个setter或getter方法，可以使课堂只读或只写。换句话说，你可以跳过getter或setter方法。
它为你提供了数据的控制。假设你想设置id的值应该是大于100只，你可以写setter方法内部的逻辑。你可以写逻辑不是负数存储在setter方法。
它是一种实现Java数据隐藏，因为其他类将不能够通过私有数据成员访问数据。
包囊类很容易测试。因此，它是单元测试更好。
该标准的IDE都提供工具来生成getter和setter。因此，很容易和快速地使用Java创建封装类。
在Java中封装的简单示例
让我们来看看封装的简单的例子，只有一个与它的setter和getter方法场。
文件：Student.java

//A Java class which is a fully encapsulated class. //It has a private data member and getter and setter methods. package com.srcmini; public class Student{ //private data member private String name; //getter method for name public String getName(){ return name; } //setter method for name public void setName(String name){ this.name=name } }

文件：Test.java

//A Java class to test the encapsulated class. package com.srcmini; class Test{ public static void main(String[] args){ //creating instance of the encapsulated class Student s=new Student(); //setting value in the name member s.setName("vijay"); //getting value of the name member System.out.println(s.getName()); } }

Compile By: javac -d . Test.java Run By: java com.srcmini.Test

输出：

vijay

只读类

//A Java class which has only getter methods. public class Student{ //private data member private String college="AKG"; //getter method for college public String getCollege(){ return college; } }

现在，你不能改变的高校数据成员，这是“AKG”的价值。

s.setCollege("KITE"); //will render compile time error

只写类

//A Java class which has only setter methods. public class Student{ //private data member private String college; //getter method for college public void setCollege(String college){ this.college=college; } }

现在，你不能让大学的价值，你只能改变大学的数据成员的值。

System.out.println(s.getCollege()); //Compile Time Error，because there is no such method System.out.println(s.college); //Compile Time Error，because the college data member is private. //So，it can't be accessed from outside the class

在Java中封装的另一实施例
让我们看到，只有四个拥有setter和getter方法封装领域的另一个例子。
文件：Account.java

//A Account class which is a fully encapsulated class. //It has a private data member and getter and setter methods. class Account { //private data members private long acc_no; private String name，email; private float amount; //public getter and setter methods public long getAcc_no() { return acc_no; } public void setAcc_no(long acc_no) { this.acc_no = acc_no; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public float getAmount() { return amount; } public void setAmount(float amount) { this.amount = amount; }}

文件：TestAccount.java

//A Java class to test the encapsulated class Account. public class TestEncapsulation { public static void main(String[] args) { //creating instance of Account class Account acc=new Account(); //setting values through setter methods acc.setAcc_no(7560504000L); acc.setName("Sonoo Jaiswal"); acc.setEmail("sonoojaiswal@srcmini.com"); acc.setAmount(500000f); //getting values through getter methods System.out.println(acc.getAcc_no()+" "+acc.getName()+" "+acc.getEmail()+" "+acc.getAmount()); } }

输出：