前言:
眼前朋友们对“java创建一个对象”都比较讲究,兄弟们都需要剖析一些“java创建一个对象”的相关内容。那么小编在网络上网罗了一些有关“java创建一个对象””的相关文章,希望同学们能喜欢,姐妹们快快来学习一下吧!在本篇文章中,将介绍5种创建Java对象的方式。类是创建对象的基本模板,接下来将介绍5种不同的方式,利用Java类来实例化Java对象。
1. 使用new关键字
采用new关键字实例化对象是Java中最为常见的方法,下面是采用new关键字实例化对象的示例。在开始之前,我们先准备好一个Java类:Student.java。
package com.ramostear.oops;public class Student{ private String name; private String nickname; public Student(String name,String nickname){ this.name = name; this.nickname = nickname; } public String getName(){ return name; } public void setName(String name){ this.name = name; } public String getNickname(){ return nickname; } public void setNickname(String nickname){ this.nickname = nickname; }}
接下来,我们通过new关键字来创建几个学生:
package com.ramostear.oops;public class TestNewStudent{ public static void main(String[] args){ Student zhangsan = new Student("Zhangsan","张三"); Student lisi = new Student(); lisi.setName("Lisi"); lisi.setNickname("李四"); }}2. 使用Class类的newInstance()方法
首先,我们可以通过Class.forName()方法动态加载目标类,然后再调用newInstance()方法,动态实例化对象。同理,在开始之前,我们需要准备一个目标类:Student.java。
package com.ramostear.oops;public class Student{ private String name = "Zhangsan"; private String nickname = "张三"; public Student(){ super(); } public Student(String name,String nickname){ super(); this.name = name; this.nickname = nickname; } public String getName(){ return name; } public void setName(String name){ this.name = name; } public String getNickname(){ return nickname; } public void setNickname(String nickname){ this.nickname = nickname; }}
接下来,将演示如何通过newInstance()方法来创建新的对象:
package com.ramostear.oops;public class TestUseNewInstanceMethod{ public static void main(String[] args){ try{ String className = "com.ramostear.oops.Student"; Class clz = Class.forName(className); Student student = (Student) clz.newInstance(); System.out.println("student name :"+ student.getName()+", nickname: "+student.getNickname()); }catch(InstantiationException | IllegalAccessException | ClassNotFoundException e){ e.printStackTrace(); } }}
运行main()方法,将输出如下信息:
student name :Zhangsan, nickname:张三3. 使用Constructor.newInstance()方法
与Class类的newInstance()方法相似,我们还可以使用java.lang.reflect.Constructor类的newInstance()方法来创建新的对象。同样,我们先准备一个目标类:
package com.ramostear.oops;public class Student{ private String name = "Constructor"; private String nickname = "构造器"; public Student(){ super(); } public Student(String name,String nickname){ super(); this.name = name; this.nickname = nickname; } public String getName(){ return name; } public void setName(String name){ this.name = name; } public String getNickname(){ return nickname; } public void setNickname(String nickname){ this.nickname = nickname; }}
接下来,我们看看如何使用Constructor的newInstance()方法创建新的对象:
package com.ramostear.oops;import java.lang.reflect.Constructor;import java.lang.reflect.InvocationTargetException;public class UseConstructorNewInstanceMethod{ public static void main(String[] args){ Constructor<Student> studentConstructor; try{ studentConstructor = Student.class.getConstructor(); Student student = studentConstructor.newInstance(); System.out.println("student name :"+ student.getName()+", nickname: "+student.getNickname()); }catch(InstantiationException | IllegalAccessException | IllegalArgumentException | InvocationTargetException | NoSuchMethodException | SecurityException e){ e.printStackTrace(); } } }
执行main()方法,将在控制台输出如下信息:
student name:Constructor, nickname:构造器4. 使用反序列化
如果要使用反序列化创建对象,则目标类首先要实现Serializable接口。Serializable是一个标记接口。在本次示例中,我们先创建一个Student对象,并将其保存到data.txt文件中,然后在通过反序列化操作,读取data.txt中的数据,并创建新的对象。
package com.ramostear.oops;import java.io.Serializable;public class Student implements Serializable{ private String name; private String nickname; public Student() { super(); } public Student(String name, String nickname) { super(); this.name = name; this.nickname = nickname; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getNickname() { return nickname; } public void setNickname(String nickname) { this.nickname = nickname; }}
接下来,将通过一个简单的示例,演示如何使用反序列化的方式创建新的对象:
package com.ramostear.oops;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.ObjectInputStream;import java.io.ObjectOutputStream;public class StudentDemo { public static void main(String[] args) { String filePath = "data.txt"; Student student1 = new Student("Deserialization", "反序列化"); try { FileOutputStream fileOutputStream = new FileOutputStream(filePath); ObjectOutputStream outputStream = new ObjectOutputStream(fileOutputStream); outputStream.writeObject(student1); outputStream.flush(); outputStream.close(); FileInputStream fileInputStream = new FileInputStream(filePath); ObjectInputStream inputStream = new ObjectInputStream(fileInputStream); Student student2 = (Student) inputStream.readObject(); inputStream.close(); System.out.println("Student name:"+student2.getName()+", nickname:"+student2.getNickname()); } catch (Exception ee) { ee.printStackTrace(); } }}
执行上述代码,将在控制台输出如下信息:
Student name:Deserialization,nickname:反序列化5. 使用对象克隆创建新的对象
clone()方法可以创建现有对象的副本,但在使用clone()方法前,需保证模板类实现了Cloneable接口,Cloneable接口也是一个标记类接口。下面是使用克隆方式创建新对象的完整示例:
package net.javaguides.corejava.oops;import java.io.Serializable;public class Student implements Cloneable { private String name; private String nickname; public Student() { super(); } public Student(String name, String nickname) { super(); this.name = name; this.nickname = nickname; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getNickname() { return nickname; } public void setNickname(String nickname) { this.nickname = nickname; } public static void main(String args[]) { Student stu1 = new Student("Clone", "克隆"); try { Student stu2 = (Student) stu1.clone(); System.out.println("Student name :"+stu2.getName()+",nickname:"+stu2.getNickanme()); } catch (CloneNotSupportedException e) { e.printStackTrace(); } }}
运行上述代码,控制台将输出如下信息:
Student name: Clone,nickname:克隆
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